feat(run,notifications,profiles): stop sending prompts nobody typed, and fix notification + profile delivery

Run console:
- Picking a pipeline no longer pre-writes anything into the prompt box
  (`promptPrefill` in `LaneConsolePane.tsx` is gone — it wrote the driving
  slash command on a claude lane and a stage checklist on a codex one).
  Whatever sits in that box is sent as a real prompt the moment the run
  starts, so the box is the user's alone now.
- Resuming a session sends NO prompt at all (`handleStart` in `RunSetup.tsx`):
  the resumed session carries its own transcript, and leftover text in the box
  fired an extra turn into it.

Notifications:
- `client/src/lib/notify.ts` is now the ONE sender, used by both
  `useNotifications` and Settings' test button, and it reports where the
  notification landed: `POST /api/push/send` answering `{native:false,pushed:0}`
  means it went NOWHERE, so the client falls back to a local notification
  instead of counting the 200 as delivered.
- A notification carries the lane that raised it (`/workspace?lane=<id>`), and
  Workspace selects that lane on arrival.

Profiles:
- `server/lib/cc-profiles.js` reads and writes the macOS login Keychain item
  `Claude Code-credentials`, where the `claude` CLI actually keeps
  `claudeAiOauth` on darwin — a switch used to rewrite a file nothing reads.
  The file stays the fallback, is kept in step only when it already exists, and
  `AGENTHUB_CC_KEYCHAIN=0` pins it (tests set it).

Tests: npm run test:server (1820 pass), client vitest (553 pass).

client/src/hooks/__tests__/useNotifications.test.ts

@@ -36,7 +36,9 @@ describe("useNotifications", () => {
     localStorage.clear();
     // notify() posts to /api/push/send first and only falls back to a local
     // Notification when that throws, so the fetch spy is what we assert on.
-    fetchMock = vi.fn().mockResolvedValue({ ok: true });
+    fetchMock = vi
+      .fn()
+      .mockResolvedValue({ ok: true, json: async () => ({ ok: true, native: true, pushed: 1 }) });
     vi.stubGlobal("fetch", fetchMock);
     vi.stubGlobal(
       "Notification",
@@ -76,6 +78,32 @@ describe("useNotifications", () => {
     expect(sentTitles()[0]).toBe("Claude Finished Responding");
   });
 
+  it("shows a local notification when the push landed nowhere", async () => {
+    // What a browser with no push subscription gets back: HTTP 200, zero
+    // deliveries. Before this, the 200 alone counted as success and the user
+    // saw nothing at all.
+    fetchMock.mockResolvedValue({
+      ok: true,
+      json: async () => ({ ok: true, native: false, pushed: 0, failed: 0 }),
+    });
+    enable();
+    renderHook(() => useNotifications());
+
+    emit("Stop", "Done");
+    await vi.waitFor(() => expect(Notification).toHaveBeenCalledTimes(1));
+    expect(vi.mocked(Notification).mock.calls[0]?.[0]).toBe("Claude Finished Responding");
+  });
+
+  it("does not double up when the push was delivered", async () => {
+    enable();
+    renderHook(() => useNotifications());
+
+    emit("Stop", "Done");
+    await vi.waitFor(() => expect(sentTitles()).toHaveLength(1));
+    await new Promise((r) => setTimeout(r, 20));
+    expect(Notification).not.toHaveBeenCalled();
+  });
+
   it("stays silent while notifications are disabled", async () => {
     renderHook(() => useNotifications());