feat: native diff surface — QuickDiff + cowriting-baseline: provider + Review Changes + status bar (spec §6.4, INV-13)

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

src/extension.ts

@@ -16,6 +16,7 @@ import { LiveProgressUi } from "./liveProgressUi";
 import { EditorProposalController } from "./editorProposalController";
 import { isAuthorable, routeEdit, selectionRejection } from "./workspacePath";
 import { CoeditingRegistry } from "./coeditingRegistry";
+import { ScmSurfaceController } from "./scmSurface";
 
 const CHANNEL_NAME = "Cowriting (Cline SDK)";
 
@@ -30,6 +31,7 @@ export interface CowritingApi {
   liveProgressUi: LiveProgressUi;
   editorProposalController: EditorProposalController;
   coeditingRegistry: CoeditingRegistry;
+  scmSurfaceController: ScmSurfaceController;
 }
 
 export function activate(context: vscode.ExtensionContext): CowritingApi | undefined {
@@ -105,6 +107,23 @@ export function activate(context: vscode.ExtensionContext): CowritingApi | undef
   const diffViewController = new DiffViewController(baselineStore, gitBaseline, coeditingRegistry);
   context.subscriptions.push(diffViewController);
 
+  // Task 1 hook: expose the resolved baseline mode ("head"/"snapshot") to the
+  // registry's context-key sync, and re-sync `cowriting.baselineMode` whenever
+  // a baseline is (re)captured (entry, head-refresh, pin) — the "Mark Changes
+  // as Reviewed" menu entry (snapshot-only, Task 3) is gated on that key.
+  coeditingRegistry.baselineModeOf = (uri) => diffViewController.modeOf(uri.toString());
+  context.subscriptions.push(
+    diffViewController.onDidChangeBaseline(() => coeditingRegistry.syncContext(vscode.window.activeTextEditor)),
+  );
+
+  // --- Task 3: the native diff surface (spec §6.4/§5, INV-13) — QuickDiff
+  // gutter bars, the cowriting-baseline: content provider, "Review Changes",
+  // and the status-bar change count. Constructed after diffViewController
+  // (consumes getBaseline/modeOf/onDidChangeBaseline) and the registry
+  // (consumes isCoediting/onDidChange), gated on INV-10. ---
+  const scmSurfaceController = new ScmSurfaceController(coeditingRegistry, diffViewController);
+  context.subscriptions.push(scmSurfaceController);
+
   // F8: the out-of-workspace/untitled authoring sidecar — same GLOBAL storage
   // home as the F6 baseline, keyed by sha256(uri) (INV-19/24). Constructed
   // workspace-independently; the router falls back to it for any non-in-folder
@@ -396,6 +415,7 @@ export function activate(context: vscode.ExtensionContext): CowritingApi | undef
     liveProgressUi,
     editorProposalController,
     coeditingRegistry,
+    scmSurfaceController,
   };
 }