F3 SLICE-5: live claude-code turn via applyAgentEdit seam + manual smoke (INV-8) (#6)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/extension.ts

@@ -81,6 +81,56 @@ export function activate(context: vscode.ExtensionContext): CowritingApi | undef
     ),
   );
 
+  // F3 SLICE-5: the live turn (PUC-2) — selection + instruction → one
+  // claude-code SDK turn (liveTurn.ts, INV-8) → the applyAgentEdit seam (INV-9).
+  context.subscriptions.push(
+    vscode.commands.registerCommand("cowriting.editSelection", async () => {
+      const editor = vscode.window.activeTextEditor;
+      if (!editor || editor.selection.isEmpty || !editor.document.uri.fsPath.startsWith(root)) {
+        void vscode.window.showWarningMessage("Cowriting: select some text in a workspace document first.");
+        return;
+      }
+      const instruction = await vscode.window.showInputBox({
+        prompt: "What should Claude do with the selection?",
+        placeHolder: "e.g. tighten this paragraph",
+      });
+      if (!instruction) return;
+      const document = editor.document;
+      const selection = editor.selection;
+      const expectedVersion = document.version;
+      const selectedText = document.getText(selection);
+      const turnId = `turn-${Date.now().toString(36)}`;
+      try {
+        await vscode.window.withProgress(
+          { location: vscode.ProgressLocation.Notification, title: "Cowriting: asking Claude…" },
+          async () => {
+            const { runEditTurn } = await import("./liveTurn");
+            const turn = await runEditTurn(instruction, selectedText);
+            const ok = await attributionController.applyAgentEdit(
+              document,
+              new vscode.Range(selection.start, selection.end),
+              turn.replacement,
+              {
+                kind: "agent",
+                id: "claude",
+                agent: { sdk: "@cline/sdk", model: turn.model, sessionId: turn.sessionId },
+              },
+              { expectedVersion, turnId },
+            );
+            if (!ok) {
+              void vscode.window.showWarningMessage(
+                "Cowriting: the document changed while Claude was editing — nothing was applied.",
+              );
+            }
+          },
+        );
+      } catch (err) {
+        const message = err instanceof Error ? err.message : String(err);
+        void vscode.window.showErrorMessage(`Cowriting: Claude edit failed — ${message}`);
+      }
+    }),
+  );
+
   // Render threads + attributions for already-open editors, and on future opens.
   const renderIfOpen = (doc: vscode.TextDocument) => {
     if (doc.uri.scheme === "file" && doc.uri.fsPath.startsWith(root)) {