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it works" is rewritten as the native-surface map; the superseded F6/F7/F9/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/f12InlineDiff.test.ts

@@ -12,7 +12,7 @@ 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 && api?.proposalController, "exports controllers");
+  assert.ok(api?.diffViewController && api?.proposalController, "exports controllers");
   return api;
 }
 
@@ -34,8 +34,6 @@ suite("F12 inline diff — seam landBaseline (#64, INV-48)", () => {
   test("applyAgentEdit with landBaseline:false applies text but does NOT advance the baseline", async () => {
     const { doc, key } = await freshDoc("docs/f12-land.md", "# T\n\nalpha here.\n");
     const api = await getApi();
-    await vscode.commands.executeCommand("cowriting.showTrackChangesPreview");
-    await settle();
     const before = api.diffViewController.getBaseline(key)?.text ?? doc.getText();
     const start = doc.getText().indexOf("alpha");
     const ok = await api.attributionController.applyAgentEdit(
@@ -171,23 +169,25 @@ suite("F12 inline diff — editor surface (#64, INV-48/52)", () => {
 });
 
 suite("F12 inline diff — control parity (#64, INV-53)", () => {
-  test("reject from the webview reverts in place; rejectAll clears every proposal", async () => {
-    const { doc, key } = await freshDoc("docs/f12-parity.md", "# P\n\nuno aaa.\n\ndos bbb.\n");
+  test("reject-one via revertInPlace reverts in place; rejectAll clears every proposal", async () => {
+    const { doc } = await freshDoc("docs/f12-parity.md", "# P\n\nuno aaa.\n\ndos bbb.\n");
     const api = await getApi();
-    const ctl = api.trackChangesPreviewController;
+    const p = api.proposalController;
     const editFlow = api.editFlow;
-    await vscode.commands.executeCommand("cowriting.showTrackChangesPreview");
-    await settle();
     editFlow.setEditTurnForTest(async () => ({ replacement: "# P\n\nuno AAA.\n\ndos BBB.\n", model: "m", sessionId: "s" }));
     const ids = await editFlow.runEditAndPropose(doc, { kind: "document" }, "up");
     await settle(); await settle();
     assert.ok(doc.getText().includes("AAA") && doc.getText().includes("BBB"));
-    // reject ONE via the webview intent → that block reverts, the other stays applied
-    ctl.receiveMessage(key, { type: "reject", proposalId: ids[0] });
+    // reject ONE via the same seam the per-proposal "✗ Reject" CodeLens uses
+    // (Task 8, PUC-2) → that block reverts, the other stays applied.
+    const docKey = p.keyFor(doc);
+    assert.ok(await p.revertInPlace(docKey, ids[0]), "revert one proposal");
     await settle(); await settle();
     assert.ok(doc.getText().includes("uno aaa.") && doc.getText().includes("BBB"), "one reverted, one applied");
-    // rejectAll via the command → all gone, document restored
-    ctl.receiveMessage(key, { type: "rejectAll" });
+    // rejectAll via the same seam the top-of-file "✗ Reject all" CodeLens uses →
+    // all gone, document restored.
+    const { reverted } = await p.rejectAll(doc);
+    assert.strictEqual(reverted, 1, "the one remaining proposal reverted");
     await settle(); await settle();
     assert.strictEqual(doc.getText(), "# P\n\nuno aaa.\n\ndos bbb.\n", "document restored");
     assert.strictEqual(api.proposalController.listProposals(doc).length, 0);