feat!: sunset the review-panel webview — built-in preview + native diff are the review surfaces (D3/D17, spec §6.10); Keep/Reject lens copy (PUC-2)

Deletes the last bespoke UI surface (TrackChangesPreviewController + its
sealed webview client assets); every entry point re-points at native VS
Code chrome per spec §5: the #41 right-click entries become
cowriting.openReviewPreview (enter coediting if needed -> "Open Preview to
the Side"), Ctrl+Alt+R/Cmd+Alt+R moves to cowriting.reviewChanges (native
diff), and the F12 CodeLens per-proposal titles read "Keep"/"Reject" with
a top-of-file "Keep all (N)"/"Reject all" pair once >=2 proposals are
pending. EditFlow drops its own askClaude/askEditInstruction (the
webview's only caller) and its now-unused constructor params.

Coverage that lived only in the webview's test seams (renderHtmlFor,
receiveMessage, isOpen, ...) moves to direct calls against the surviving
controllers/pure renderReview (test/e2e/suite/helpers.ts gains a shared
renderHtmlFor probe); a genuine gap (pending-proposal + unchanged-block
rendering) is backfilled in test/previewAnnotations.test.ts. README's "how
it works" is rewritten as the native-surface map; the superseded F6/F7/F9/
F10/F11 sections are kept as a marked historical record rather than
deleted outright.

292 unit + 91 E2E green.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

test/e2e/suite/authorship.test.ts

@@ -3,6 +3,7 @@ import * as fs from "fs";
 import * as path from "path";
 import * as vscode from "vscode";
 import type { CowritingApi } from "../../../src/extension";
+import { renderHtmlFor } from "./helpers";
 
 const WS = process.env.E2E_WORKSPACE!;
 const settle = () => new Promise((r) => setTimeout(r, 300));
@@ -10,7 +11,7 @@ const settle = () => new Promise((r) => setTimeout(r, 300));
 async function getApi(): Promise<CowritingApi> {
   const ext = vscode.extensions.getExtension("benstull.vscode-cowriting-plugin")!;
   const api = (await ext.activate()) as CowritingApi;
-  assert.ok(api?.trackChangesPreviewController && api?.proposalController, "exports preview + proposal");
+  assert.ok(api?.attributionController && api?.proposalController, "exports attribution + proposal");
   return api;
 }
 
@@ -20,14 +21,16 @@ async function getApi(): Promise<CowritingApi> {
 // suite checks that render BEFORE accepting (the class to check is cw-ins-claude,
 // the proposal block, NOT cw-by-claude — the old F9 authorship render) and that
 // the attribution data layer survives the accept; it does not exercise the F6
-// baseline (see diffView.test.ts / trackChangesPreview.test.ts / baselineRouter.test.ts
-// for the post-accept baseline behavior, INV-7/D21). Owns its own markdown doc.
+// baseline (see diffView.test.ts / baselineRouter.test.ts for the post-accept
+// baseline behavior, INV-7/D21). Owns its own markdown doc. Task 8: the render
+// probe is now the pure `renderReview` directly (the webview that used to wrap
+// it, `renderHtmlFor`, is gone).
 suite("F10 review preview — pending Claude proposal renders cw-ins-claude in the on-state (host E2E, no LLM)", () => {
   const DOC_REL = "docs/f10claude.md";
   const TARGET = "The sentence Claude will compose over.";
   const REPLACEMENT = "The sentence CLAUDE COMPOSED via the seam.";
 
-  test("a pending Claude proposal carries cw-ins-claude; accepted proposal leaves attribution data intact; mode defaults to on", async () => {
+  test("a pending Claude proposal carries cw-ins-claude; accepted proposal leaves attribution data intact", async () => {
     const abs = path.join(WS, DOC_REL);
     fs.mkdirSync(path.dirname(abs), { recursive: true });
     fs.writeFileSync(abs, `# F10\n\n${TARGET}\n`, "utf8");
@@ -41,12 +44,6 @@ suite("F10 review preview — pending Claude proposal renders cw-ins-claude in t
     const api = await getApi();
     const key = uri.toString();
 
-    // open the preview — annotations default ON (F10/INV-33)
-    await vscode.commands.executeCommand("cowriting.showTrackChangesPreview");
-    await settle();
-    assert.ok(api.trackChangesPreviewController.isOpen(key), "preview open");
-    assert.strictEqual(api.trackChangesPreviewController.getMode(key), "on", "annotations default to on");
-
     // Claude proposes via the seam (F12 optimistic-apply; proposal stays PENDING)
     const start = doc.getText().indexOf(TARGET);
     const id = await vscode.commands.executeCommand<string>("cowriting.proposeAgentEdit", {
@@ -64,7 +61,7 @@ suite("F10 review preview — pending Claude proposal renders cw-ins-claude in t
     // PENDING proposal: the preview renders the proposal block with cw-ins-claude.
     // After accepting, the baseline advances (INV-18) → the text becomes "unchanged"
     // and renders plain — so we check BEFORE accepting.
-    const pendingHtml = api.trackChangesPreviewController.renderHtmlFor(key);
+    const pendingHtml = renderHtmlFor(api, doc, key);
     assert.ok(
       pendingHtml.includes("cw-ins-claude"),
       "pending Claude proposal block carries cw-ins-claude in the on-state render",