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it works" is rewritten as the native-surface map; the superseded F6/F7/F9/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/s48PinClean.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, 400));
@@ -10,7 +11,7 @@ const settle = () => new Promise((r) => setTimeout(r, 400));
 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, "exports preview controller");
+  assert.ok(api?.diffViewController && api?.attributionController, "exports diffView + attribution");
   return api;
 }
 
@@ -35,21 +36,19 @@ suite("S48 — pin → fully clean review panel (host E2E, no LLM)", () => {
   test("pin clears authorship coloring; a later edit brings annotations back", async () => {
     const { doc, key } = await freshDoc("docs/s48pin.md", "# S48\n\nAn original baseline paragraph.\n");
     const api = await getApi();
-    const ctl = api.trackChangesPreviewController;
-    await vscode.commands.executeCommand("cowriting.showTrackChangesPreview");
-    await settle();
 
     // Type a paragraph → a human attribution span + author coloring in the on-state.
     const edit = new vscode.WorkspaceEdit();
     edit.insert(doc.uri, doc.positionAt(doc.getText().length), "\n\nA freshly typed human paragraph.\n");
     assert.ok(await vscode.workspace.applyEdit(edit), "operator edit applied");
     await settle();
-    assert.match(ctl.renderHtmlFor(key), /cw-ins-human/, "typed text is author-colored cw-ins-human before the pin");
+    assert.match(renderHtmlFor(api, doc, key), /cw-ins-human/, "typed text is author-colored cw-ins-human before the pin");
 
-    // Pin the baseline → zero diff → the panel must be fully clean.
-    ctl.receiveMessage(key, { type: "pinBaseline" });
+    // Pin the baseline (the real command — replaces the F11-webview's pinBaseline
+    // toolbar intent, Task 8) → zero diff → the render must be fully clean.
+    await vscode.commands.executeCommand("cowriting.markReviewed");
     await settle();
-    const pinned = ctl.renderHtmlFor(key);
+    const pinned = renderHtmlFor(api, doc, key);
     assert.ok(!pinned.includes("cw-ins-human"), "no human insertion marks after pin");
     assert.ok(!pinned.includes("cw-ins-claude"), "no Claude insertion marks after pin");
     assert.ok(!pinned.includes("cw-ins-") && !pinned.includes("cw-del-"), "no insertion or deletion marks after pin");
@@ -61,6 +60,6 @@ suite("S48 — pin → fully clean review panel (host E2E, no LLM)", () => {
     edit2.insert(doc.uri, doc.positionAt(doc.getText().length), "\n\nA second typed paragraph diverges again.\n");
     assert.ok(await vscode.workspace.applyEdit(edit2), "second operator edit applied");
     await settle();
-    assert.match(ctl.renderHtmlFor(key), /cw-ins-human/, "cw-ins-human authorship coloring returns once the doc diverges from the pin");
+    assert.match(renderHtmlFor(api, doc, key), /cw-ins-human/, "cw-ins-human authorship coloring returns once the doc diverges from the pin");
   });
 });