Contribute rewrite Phase 7: retire DiffView

The Phase 3 preview-pane inline overlay and Phase 4 raw-pane gutter
accent together cover the review affordance DiffView was the interim
home for, so the toolbar toggle collapses and the surface goes.

- frontend/src/components/DiffView.jsx deleted.
- RFCView.jsx: drop the DiffView + marked imports, the reviewMode /
  reviewHTML state, the toggleReviewMode callback, the "Review changes"
  toolbar button, and the reviewMode ternary in render. editorEditable
  simplifies to mode === 'contribute' && canContribute. File-header
  docstring updated: "DiffView" → "preview-pane tracked-change overlay
  (§8.10)".
- App.css: remove the .diff-view-wrapper and .diff-view-empty rules;
  relabel the DiffView section header as ChangeTooltip (which lives on
  as the Phase 3 overlay's hover affordance). Drop the dead .editor-
  content .tiptap rules — Tiptap had no remaining consumers after
  DiffView's deletion. The Contribute toolbar still renders the
  accepted/pending hint + Phase 6 Chat toggle; only the Review-changes
  button is removed.
- MarkdownPreview.jsx: comment updated to drop the DiffView mention
  from the scoped-Marked-instance rationale.
- SPEC.md: §8.10 retitled "Tracked-change markup" (was "...and the
  review-mode toggle"); the legacy-DiffView paragraph rewritten as a
  one-sentence retirement note. §8.1, §8.15, §9.4, §9.5 references to
  DiffView / review-mode cleaned up. §19.2's persistent-accepted-change
  candidate updated to point at the preview-pane overlay rather than
  DiffView.

No DiffView orphans remain (grep confirms .btn-review-toggle is still
the Discuss-mode "Show tracked changes" toggle, ChangeTooltip and
trackedOverlay carry historical comments only, PRView's §19.2 comment
is unrelated). Frontend reload shows no console errors.

Backend integration suite: 125 passed.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

frontend/src/App.css

@@ -431,31 +431,6 @@
 .editor-content {
   max-width: 720px; margin: 0 auto; outline: none;
 }
-.editor-content .tiptap {
-  outline: none; font-size: 15px; line-height: 1.75; color: #1a1a1a;
-}
-.editor-content .tiptap h1 { font-size: 22px; font-weight: 700; margin: 24px 0 12px; }
-.editor-content .tiptap h2 { font-size: 17px; font-weight: 600; margin: 20px 0 8px; }
-.editor-content .tiptap h3 { font-size: 15px; font-weight: 600; margin: 16px 0 6px; }
-.editor-content .tiptap p { margin: 0 0 12px; }
-.editor-content .tiptap ul, .editor-content .tiptap ol { padding-left: 24px; }
-.editor-content .tiptap code { background: #f0f0ee; padding: 1px 5px; border-radius: 3px; font-size: 13px; }
-
-.editor-content .tiptap .selection-highlight {
-  background: rgba(99, 102, 241, 0.15);
-  border-radius: 2px;
-  outline: 1px solid rgba(99, 102, 241, 0.3);
-  outline-offset: 1px;
-}
-.editor-content .tiptap .tracked-delete {
-  background: #fee2e2; color: #991b1b; text-decoration: line-through;
-  border-radius: 2px; padding: 1px 2px; cursor: pointer;
-}
-.editor-content .tiptap .tracked-insert {
-  background: #dcfce7; color: #166534;
-  border-radius: 2px; padding: 1px 2px; cursor: pointer;
-}
-
 /* CodeMirror 6 source editor (Contribute mode). */
 .cm-source-editor {
   flex: 1; min-height: 0;
@@ -540,11 +515,11 @@
   background: rgba(99, 102, 241, 0.22);
 }
 
-/* Tracked-change overlay (Phase 3, §8.10) — preview-pane equivalents of
-   the .editor-content .tiptap rules above. The Contribute pane shows
-   these by default; the Discuss pane gates them behind a toolbar
-   toggle. Hovering surfaces a ChangeTooltip with the source message
-   and reason. */
+/* Tracked-change overlay (Phase 3, §8.10) — green/red decorations on
+   accepted-change spans inside the rendered preview. The Contribute
+   pane shows these by default; the Discuss pane gates them behind a
+   toolbar toggle. Hovering surfaces a ChangeTooltip with the source
+   message and reason. */
 .markdown-preview .tracked-delete {
   background: #fee2e2; color: #991b1b; text-decoration: line-through;
   border-radius: 2px; padding: 1px 2px; cursor: pointer;
@@ -1057,16 +1032,9 @@
   font-size: 13px; font-weight: 600; cursor: pointer;
 }
 
-/* ── DiffView ──────────────────────────────────────────────────── */
+/* ── ChangeTooltip (shared between the Phase 3 preview-pane overlay
+   and the §8.10 hover affordance) ─────────────────────────────────── */
 
-.diff-view-wrapper {
-  flex: 1; overflow-y: auto;
-  padding: 32px 48px;
-}
-.diff-view-empty {
-  font-size: 13px; color: #999;
-  text-align: center; padding: 24px;
-}
 .diff-tooltip {
   background: #fff; border: 1px solid #e5e5e5;
   border-radius: 8px; padding: 10px 12px;

frontend/src/components/DiffView.jsx

@@ -1,48 +0,0 @@
-// DiffView.jsx — the §8.10 read-only render surface for accepted changes.
-//
-// In contribute mode, a toolbar toggle replaces the editor with this
-// view. We reconstruct the markup for every accepted change in branch
-// history by reading the `changes` table (passed in as `changes`) plus
-// the current rendered HTML; hovering any tracked span surfaces a
-// tooltip with the change's type/model/prompt/reason context.
-
-import { useState, useCallback } from 'react'
-import ChangeTooltip from './ChangeTooltip.jsx'
-
-export default function DiffView({ html, changes, messages }) {
-  const [tooltip, setTooltip] = useState(null)
-  const handleMouseMove = useCallback((e) => {
-    const span = e.target.closest('[data-change-id]')
-    if (span) {
-      const id = span.getAttribute('data-change-id')
-      const change = changes.find(c => String(c.id) === String(id))
-      if (change) {
-        setTooltip({ change, position: { x: e.clientX, y: e.clientY } })
-        return
-      }
-    }
-    setTooltip(null)
-  }, [changes])
-
-  const acceptedCount = changes.filter(c => c.state === 'accepted').length
-
-  return (
-    <div className="diff-view-wrapper">
-      {acceptedCount === 0 && (
-        <div className="diff-view-empty">
-          No accepted changes yet on this branch. Accept proposals from the
-          change panel to see them rendered here in place.
-        </div>
-      )}
-      <div className="editor-content">
-        <div
-          className="tiptap diff-view-document"
-          onMouseMove={handleMouseMove}
-          onMouseLeave={() => setTooltip(null)}
-          dangerouslySetInnerHTML={{ __html: html }}
-        />
-      </div>
-      {tooltip && <ChangeTooltip change={tooltip.change} messages={messages} position={tooltip.position} />}
-    </div>
-  )
-}

frontend/src/components/MarkdownPreview.jsx

@@ -49,7 +49,7 @@ function escapeHtml(s) {
 }
 
 // Scoped Marked instance so the mermaid-fence renderer doesn't leak
-// to other call sites (Editor.jsx, DiffView review HTML, etc.).
+// to any other call site that might construct its own Marked.
 const previewMarked = new Marked({
   renderer: {
     code({ text, lang }) {

frontend/src/components/RFCView.jsx

@@ -6,9 +6,10 @@
 // super-drafts. The discuss-vs-contribute flip on non-main / non-edit
 // branches per §8.3 carries over unchanged.
 //
-// The active-RFC and super-draft surfaces share their editor,
-// chat, change-card, DiffView, selection-tooltip, and PR-modal
-// machinery; the only branchings are "Start Contributing" (which
+// The active-RFC and super-draft surfaces share their editor, chat,
+// change-card, preview-pane tracked-change overlay (§8.10), selection-
+// tooltip, and PR-modal machinery; the only branchings are
+// "Start Contributing" (which
 // dispatches to promote-to-branch for active main and start-edit-branch
 // for a super-draft's canonical body per §9.5) and the metadata pane
 // (super-draft-only per §9.5).
@@ -36,11 +37,9 @@ import {
 import MarkdownSourceEditor from './MarkdownSourceEditor.jsx'
 import MarkdownPreview from './MarkdownPreview.jsx'
 import SelectionTooltip from './SelectionTooltip.jsx'
-import { marked } from 'marked'
 import PromptBar from './PromptBar.jsx'
 import ChatPanel from './ChatPanel.jsx'
 import ChangePanel, { diffWords } from './ChangePanel.jsx'
-import DiffView from './DiffView.jsx'
 import PRModal from './PRModal.jsx'
 import GraduateDialog from './GraduateDialog.jsx'
 import { claimOwnership } from '../api'
@@ -92,8 +91,6 @@ export default function RFCView({ viewer }) {
   // selection is sourced from window.getSelection() inside the
   // MarkdownPreview surface — see MarkdownPreview's onSelectionChange.
   const [selection, setSelection] = useState(null)
-  const [reviewMode, setReviewMode] = useState(false)
-  const [reviewHTML, setReviewHTML] = useState('')
   // Phase 3 — Discuss-mode opt-in for the §8.10 tracked-change overlay
   // in the single-pane preview. Contribute mode is default-on (the
   // pane exists for editorial review of your own work); Discuss mode
@@ -151,7 +148,6 @@ export default function RFCView({ viewer }) {
     setChanges([])
     setPendingDiscussChanges([])
     setManualPending(null)
-    setReviewMode(false)
     setDiscussShowChanges(false)
     setSelection(null)
     setMode('discuss')
@@ -467,24 +463,6 @@ export default function RFCView({ viewer }) {
     }
   }, [])
 
-  const toggleReviewMode = useCallback(() => {
-    setReviewMode(prev => {
-      if (!prev) {
-        // CM6 is the contribute-mode editor in Phase 1, so source HTML
-        // comes from rendering the current markdown via marked. The
-        // per-session inline tracked-change spans that Tiptap accumulated
-        // are gone for now; Phase 3's preview pane is the proper home
-        // for tracked changes anyway.
-        const editor = editorRef.current
-        const md = typeof editor?.getDoc === 'function'
-          ? editor.getDoc()
-          : (branchView?.body || '')
-        setReviewHTML(marked.parse(md))
-      }
-      return !prev
-    })
-  }, [branchView])
-
   // ── Branch dropdown navigation ─────────────────────────────────────────
   const onPickBranch = useCallback((name) => {
     if (name === branchParam) return
@@ -505,7 +483,7 @@ export default function RFCView({ viewer }) {
 
   const canContribute = branchView.capabilities?.can_contribute && branchParam !== 'main'
   const canChangeSettings = branchView.capabilities?.can_change_branch_settings
-  const editorEditable = mode === 'contribute' && canContribute && !reviewMode
+  const editorEditable = mode === 'contribute' && canContribute
   const showPromptBar = !!viewer
 
   const inDiscuss = mode === 'discuss'
@@ -671,14 +649,6 @@ export default function RFCView({ viewer }) {
           )}
           {showContributeToolbar && (
             <div className="editor-toolbar">
-              <button
-                type="button"
-                className={`btn-review-toggle${reviewMode ? ' active' : ''}`}
-                onClick={toggleReviewMode}
-                title="Toggle DiffView: read-only render of accepted changes in context"
-              >
-                {reviewMode ? '← Back to editing' : 'Review changes'}
-              </button>
               <span className="editor-toolbar-hint">
                 {changes.filter(c => c.state === 'accepted').length} accepted ·{' '}
                 {pendingCount} pending
@@ -722,64 +692,58 @@ export default function RFCView({ viewer }) {
               />
             </div>
           )}
-          {reviewMode ? (
-            <DiffView html={reviewHTML} changes={changes} messages={messages} />
-          ) : (
-            <>
-              {editorEditable ? (
-                <div className="editor-split">
-                  <div className="editor-split-pane editor-split-raw">
-                    <MarkdownSourceEditor
-                      initialDoc={editorContent}
-                      editorRef={editorRef}
-                      onUpdate={handleEditorDocUpdate}
-                    />
-                  </div>
-                  <div className="editor-split-pane editor-split-preview">
-                    <MarkdownPreview
-                      content={previewContent}
-                      onSelectionChange={handleSelectionChange}
-                      changes={changes}
-                      messages={messages}
-                      showTrackedChanges
-                    />
-                  </div>
-                </div>
-              ) : (
+          {editorEditable ? (
+            <div className="editor-split">
+              <div className="editor-split-pane editor-split-raw">
+                <MarkdownSourceEditor
+                  initialDoc={editorContent}
+                  editorRef={editorRef}
+                  onUpdate={handleEditorDocUpdate}
+                />
+              </div>
+              <div className="editor-split-pane editor-split-preview">
                 <MarkdownPreview
-                  content={editorContent}
+                  content={previewContent}
                   onSelectionChange={handleSelectionChange}
-                  className="markdown-preview-solo"
                   changes={changes}
                   messages={messages}
-                  showTrackedChanges={inDiscuss && discussShowChanges}
+                  showTrackedChanges
                 />
-              )}
-              <SelectionTooltip
-                selection={selection}
-                onAsk={handleTooltipAsk}
-                onFlag={handleTooltipFlag}
-                disabled={isStreaming || !viewer}
-                models={models}
-                selectedModel={selectedModel}
-                onModelChange={setSelectedModel}
-              />
-              {showPromptBar ? (
-                <PromptBar
-                  selection={selection?.text || null}
-                  onSubmit={handlePrompt}
-                  disabled={isStreaming}
-                  models={models}
-                  selectedModel={selectedModel}
-                  onModelChange={setSelectedModel}
-                  discussMode={inDiscuss}
-                />
-              ) : (
-                <div className="readonly-bar">
-                  Read-only view. <a href="/auth/login">Sign in</a> to participate.
-                </div>
-              )}
-            </>
+              </div>
+            </div>
+          ) : (
+            <MarkdownPreview
+              content={editorContent}
+              onSelectionChange={handleSelectionChange}
+              className="markdown-preview-solo"
+              changes={changes}
+              messages={messages}
+              showTrackedChanges={inDiscuss && discussShowChanges}
+            />
+          )}
+          <SelectionTooltip
+            selection={selection}
+            onAsk={handleTooltipAsk}
+            onFlag={handleTooltipFlag}
+            disabled={isStreaming || !viewer}
+            models={models}
+            selectedModel={selectedModel}
+            onModelChange={setSelectedModel}
+          />
+          {showPromptBar ? (
+            <PromptBar
+              selection={selection?.text || null}
+              onSubmit={handlePrompt}
+              disabled={isStreaming}
+              models={models}
+              selectedModel={selectedModel}
+              onModelChange={setSelectedModel}
+              discussMode={inDiscuss}
+            />
+          ) : (
+            <div className="readonly-bar">
+              Read-only view. <a href="/auth/login">Sign in</a> to participate.
+            </div>
           )}
         </div>