Fix #8: register warning stubs when no workspace folder; F5 opens the repo. Add selection context menus (#9)

- extension.ts: with no folder open, every contributed coauthoring command now
  registers a warning stub ('open a folder first') instead of being absent —
  the palette no longer errors 'command not found'. Opening a folder reloads
  the window and re-activates with a real root.
- .vscode/launch.json: the EDH now opens the repo as its workspace, so plain
  F5 lands in a working state.
- package.json: editor/context menu entries for 'Ask Claude to Edit
  Selection' and 'Add Coauthoring Thread on Selection', shown only when text
  is highlighted in a file-scheme editor (editorHasSelection).
- E2E: second no-workspace pass (suite-no-workspace) pins the #8 regression.

Fixes #8. Fixes #9.

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

src/extension.ts

@@ -38,7 +38,28 @@ export function activate(context: vscode.ExtensionContext): CowritingApi | undef
 
   // --- F2: region-anchored threads (Feature #4) ---
   const root = vscode.workspace.workspaceFolders?.[0]?.uri.fsPath;
-  if (!root) return undefined; // no workspace → nothing to anchor against
+  if (!root) {
+    // No folder open → nothing to anchor against, but every contributed
+    // command must still exist: leave them unregistered and the palette
+    // errors with "command not found" (#8). Register warning stubs instead;
+    // opening a folder reloads the window, re-running activate with a root.
+    const stub = () =>
+      void vscode.window.showWarningMessage(
+        "Cowriting: open a folder first — coauthoring anchors threads and attribution to workspace files.",
+      );
+    for (const command of [
+      "cowriting.createThread",
+      "cowriting.reply",
+      "cowriting.resolveThread",
+      "cowriting.reopenThread",
+      "cowriting.editSelection",
+      "cowriting.toggleAttribution",
+      "cowriting.applyAgentEdit",
+    ]) {
+      context.subscriptions.push(vscode.commands.registerCommand(command, stub));
+    }
+    return undefined;
+  }
   const store = new CoauthorStore(root);
   const threadController = new ThreadController(store, root);
   context.subscriptions.push(threadController);