refactor: extract EditFlow (runEditAndPropose + editDocument) from the review webview ahead of its sunset (spec §6.10)

Moves runEditAndPropose, the askClaude gate/prompt/progress wrapper, the
EditTarget type, the editTurn/askEditInstruction/turnSeq state, and the
cowriting.editDocument command registration out of TrackChangesPreviewController
into a new EditFlow (src/editFlow.ts), reachable from the review webview
(delegates) and, from Task 6 on, the thread controller. extension.ts now
constructs EditFlow before the preview controller and routes
acceptAllProposals/rejectAllProposals directly to ProposalController, dropping
the preview-controller indirection. E2E suites that drove the old
trackChangesPreviewController.{setEditTurnForTest,runEditAndPropose,askEditInstruction}
seams now drive the same seams on editFlow.

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

src/extension.ts

@@ -12,6 +12,7 @@ import { SidecarRouter } from "./sidecarRouter";
 import { DiffViewController } from "./diffViewController";
 import { GitBaselineAdapter } from "./gitBaseline";
 import { TrackChangesPreviewController } from "./trackChangesPreview";
+import { EditFlow } from "./editFlow";
 import { LiveProgressUi } from "./liveProgressUi";
 import { EditorProposalController } from "./editorProposalController";
 import { isAuthorable, routeEdit, selectionRejection } from "./workspacePath";
@@ -29,6 +30,7 @@ export interface CowritingApi {
   versionGuard: VersionGuard;
   diffViewController: DiffViewController;
   trackChangesPreviewController: TrackChangesPreviewController;
+  editFlow: EditFlow;
   sidecarRouter: SidecarRouter;
   liveProgressUi: LiveProgressUi;
   editorProposalController: EditorProposalController;
@@ -164,17 +166,25 @@ export function activate(context: vscode.ExtensionContext): CowritingApi | undef
   );
   context.subscriptions.push(proposalController);
 
+  // --- F11/F12 (native-surfaces migration, spec §6.10): the edit flow — the
+  // `cowriting.editDocument` command, the instruction-prompt/progress-wrapped
+  // "ask Claude" gesture (INV-10 gate), and the turn→proposal(s) cut
+  // (`runEditAndPropose`, INV-39/40). Constructed BEFORE the review preview (which
+  // delegates to it) and reachable from the thread controller too (Task 6). ---
+  const editFlow = new EditFlow(proposalController, attributionController, liveProgressUi, coeditingRegistry);
+  context.subscriptions.push(editFlow);
+
   // --- F7/F10: the review preview is the single interactive review surface ---
   // Workspace-INDEPENDENT (works on any markdown doc, reuses the F6 baseline,
-  // INV-20). Constructed AFTER attribution (reads F3 spans) and proposals (routes
-  // F4 accept/reject from the webview ✓/✗).
+  // INV-20). Constructed AFTER attribution (reads F3 spans), proposals (routes
+  // F4 accept/reject from the webview ✓/✗), and editFlow (delegates the webview's
+  // askClaude toolbar intent to it).
   const trackChangesPreviewController = new TrackChangesPreviewController(
     diffViewController,
     context.extensionUri,
     attributionController,
     proposalController,
-    liveProgressUi,
-    coeditingRegistry,
+    editFlow,
   );
   context.subscriptions.push(trackChangesPreviewController);
 
@@ -189,8 +199,10 @@ export function activate(context: vscode.ExtensionContext): CowritingApi | undef
   context.subscriptions.push(editorProposalController);
 
   // #46 (INV-42): accept every pending proposal on the active doc in one gesture
-  // (also reachable from the preview toolbar's "Accept all" button). Reuses the
-  // batched F4 seam + reports applied-vs-skipped.
+  // (also reachable from the preview toolbar's "Accept all" button, which routes
+  // through its own webview-facing acceptAll). Reuses the batched F4 seam +
+  // reports applied-vs-skipped (native-surfaces migration: routes directly to
+  // ProposalController, no preview-controller indirection).
   context.subscriptions.push(
     vscode.commands.registerCommand("cowriting.acceptAllProposals", async () => {
       const doc = vscode.window.activeTextEditor?.document;
@@ -198,11 +210,17 @@ export function activate(context: vscode.ExtensionContext): CowritingApi | undef
         void vscode.window.showWarningMessage("Cowriting: open a Markdown document to accept its proposals.");
         return;
       }
-      await trackChangesPreviewController.acceptAll(doc);
+      const { applied, skipped } = await proposalController.acceptAllProposals(doc);
+      if (applied === 0 && skipped === 0) return;
+      const skipNote = skipped > 0 ? `, ${skipped} skipped (target text changed — undo or reject)` : "";
+      void vscode.window.showInformationMessage(
+        `Cowriting: accepted ${applied} proposal${applied === 1 ? "" : "s"}${skipNote}.`,
+      );
     }),
   );
 
-  // #64 (INV-53): reject every pending proposal on the active doc in one gesture.
+  // #64 (INV-53): reject every pending proposal on the active doc in one gesture
+  // (native-surfaces migration: routes directly to ProposalController).
   context.subscriptions.push(
     vscode.commands.registerCommand("cowriting.rejectAllProposals", async () => {
       const doc = vscode.window.activeTextEditor?.document;
@@ -210,7 +228,12 @@ export function activate(context: vscode.ExtensionContext): CowritingApi | undef
         void vscode.window.showWarningMessage("Cowriting: open a Markdown document to reject its proposals.");
         return;
       }
-      await trackChangesPreviewController.rejectAll(doc);
+      const { reverted } = await proposalController.rejectAll(doc);
+      if (reverted > 0) {
+        void vscode.window.showInformationMessage(
+          `Cowriting: rejected ${reverted} proposal${reverted === 1 ? "" : "s"}.`,
+        );
+      }
     }),
   );
 
@@ -319,12 +342,10 @@ export function activate(context: vscode.ExtensionContext): CowritingApi | undef
         end: document.offsetAt(selection.end),
       });
       // The instruction prompt is the multi-line split-below webview box (shared
-      // with the document case, via the preview controller); the document above
-      // keeps the selection highlighted while it's open. selectedText/fp were
-      // captured above, so moving focus to the box doesn't affect what we edit.
-      const instruction = await trackChangesPreviewController.askEditInstruction(
-        "Ask Claude to Edit This Selection",
-      );
+      // with the document case, via EditFlow); the document above keeps the
+      // selection highlighted while it's open. selectedText/fp were captured
+      // above, so moving focus to the box doesn't affect what we edit.
+      const instruction = await editFlow.askEditInstruction("Ask Claude to Edit This Selection");
       if (!instruction) return;
       const turnId = `turn-${Date.now().toString(36)}`;
       try {
@@ -433,6 +454,7 @@ export function activate(context: vscode.ExtensionContext): CowritingApi | undef
     versionGuard,
     diffViewController,
     trackChangesPreviewController,
+    editFlow,
     sidecarRouter,
     liveProgressUi,
     editorProposalController,