feat: CoeditingRegistry opt-in gate (INV-10, spec §6.4) — enter/stop commands + context keys

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

src/extension.ts

@@ -14,6 +14,7 @@ import { TrackChangesPreviewController } from "./trackChangesPreview";
 import { LiveProgressUi } from "./liveProgressUi";
 import { EditorProposalController } from "./editorProposalController";
 import { isAuthorable, routeEdit, selectionRejection } from "./workspacePath";
+import { CoeditingRegistry } from "./coeditingRegistry";
 
 const CHANNEL_NAME = "Cowriting (Cline SDK)";
 
@@ -27,6 +28,7 @@ export interface CowritingApi {
   sidecarRouter: SidecarRouter;
   liveProgressUi: LiveProgressUi;
   editorProposalController: EditorProposalController;
+  coeditingRegistry: CoeditingRegistry;
 }
 
 export function activate(context: vscode.ExtensionContext): CowritingApi | undefined {
@@ -59,6 +61,32 @@ export function activate(context: vscode.ExtensionContext): CowritingApi | undef
     }),
   );
 
+  // --- PUC-7 (native-surfaces migration): the INV-10 opt-in gate ---
+  // Every later native surface (SCM/QuickDiff, comments, preview annotations,
+  // edit commands, decorations) checks isCoediting before attaching. Persisted
+  // in workspaceState so a reload restores the set.
+  const coeditingRegistry = new CoeditingRegistry(context.workspaceState);
+  context.subscriptions.push(coeditingRegistry);
+  context.subscriptions.push(
+    vscode.commands.registerCommand("cowriting.coeditDocument", () => {
+      const ed = vscode.window.activeTextEditor;
+      if (!ed || ed.document.languageId !== "markdown" || !isAuthorable(ed.document.uri.scheme)) {
+        void vscode.window.showWarningMessage("Cowriting: open a Markdown document to coedit it.");
+        return;
+      }
+      coeditingRegistry.enter(ed.document.uri);
+      coeditingRegistry.syncContext(ed);
+    }),
+    vscode.commands.registerCommand("cowriting.stopCoediting", () => {
+      const ed = vscode.window.activeTextEditor;
+      if (!ed) return;
+      coeditingRegistry.exit(ed.document.uri);
+      coeditingRegistry.syncContext(ed);
+    }),
+    vscode.window.onDidChangeActiveTextEditor((ed) => coeditingRegistry.syncContext(ed)),
+  );
+  coeditingRegistry.syncContext(vscode.window.activeTextEditor);
+
   // --- F6: baseline data layer (Features #17 + #19) — workspace-INDEPENDENT ---
   // The two-pane vscode.diff VIEW was removed in #34 (F10's rendered preview is
   // the single review surface); only the baseline store survives, consumed by
@@ -362,6 +390,7 @@ export function activate(context: vscode.ExtensionContext): CowritingApi | undef
     sidecarRouter,
     liveProgressUi,
     editorProposalController,
+    coeditingRegistry,
   };
 }