feat(f7): register showTrackChangesPreview command + keybinding, wire controller (#21)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/extension.ts

@@ -8,6 +8,7 @@ import { buildFingerprint } from "./anchorer";
 import { VersionGuard } from "./versionGuard";
 import { BaselineStore } from "./baselineStore";
 import { DiffViewController } from "./diffViewController";
+import { TrackChangesPreviewController } from "./trackChangesPreview";
 
 const CHANNEL_NAME = "Cowriting (Cline SDK)";
 
@@ -17,6 +18,7 @@ export interface CowritingApi {
   proposalController: ProposalController;
   versionGuard: VersionGuard;
   diffViewController: DiffViewController;
+  trackChangesPreviewController: TrackChangesPreviewController;
 }
 
 export function activate(context: vscode.ExtensionContext): CowritingApi | undefined {
@@ -56,6 +58,16 @@ export function activate(context: vscode.ExtensionContext): CowritingApi | undef
   const diffViewController = new DiffViewController(baselineStore);
   context.subscriptions.push(diffViewController);
 
+  // --- F7: rendered track-changes preview (Feature #21) — workspace-INDEPENDENT ---
+  // Like F6, F7 works on any markdown doc (incl. untitled / out-of-folder), so it
+  // is constructed regardless of an open folder and its command is always live.
+  // It reuses the F6 baseline (INV-20) and adds no persistence.
+  const trackChangesPreviewController = new TrackChangesPreviewController(
+    diffViewController,
+    context.extensionUri,
+  );
+  context.subscriptions.push(trackChangesPreviewController);
+
   // --- F2: region-anchored threads (Feature #4) ---
   const root = vscode.workspace.workspaceFolders?.[0]?.uri.fsPath;
   if (!root) {
@@ -259,7 +271,14 @@ export function activate(context: vscode.ExtensionContext): CowritingApi | undef
   vscode.workspace.textDocuments.forEach(renderIfOpen);
   context.subscriptions.push(vscode.workspace.onDidOpenTextDocument(renderIfOpen));
 
-  return { threadController, attributionController, proposalController, versionGuard, diffViewController };
+  return {
+    threadController,
+    attributionController,
+    proposalController,
+    versionGuard,
+    diffViewController,
+    trackChangesPreviewController,
+  };
 }
 
 export function deactivate(): void {