fix(sim+api): proper wait loops, project switch endpoint, drop stale check

Three real fixes for the sim test + the live_gui coordination layer:

1. /api/project_switch_status endpoint in src/app_controller.py.
   The wait helper had been calling this endpoint but it did not exist;
   the helper always received a 404, fell back to {in_progress: False},
   and returned immediately even when a switch was in flight. Added the
   endpoint that reads _project_switch_in_progress, active_project_path,
   and _project_switch_error from the controller.

2. simulation/sim_base.py: replace time.sleep(2.0)/time.sleep(1.5) in
   the setup() with wait_io_pool_idle and wait_for_project_switch so
   the test does not click btn_md_only while a project switch is in
   flight. Also added the wait calls to sim_context.py for the same
   reason.

3. src/app_controller.py _handle_md_only: removed the is_project_stale()
   early-return. The stale state is a transient window during which the
   previous code dropped the click on the floor with a misleading
   'stale ui' status. The MD generation worker is safe to run from any
   project state; the action handler now always proceeds.

4. tests/test_extended_sims.py: set current_model to 'gemini-cli' so
   _do_generate does not raise KeyError('model') when the test
   overrides provider to gemini_cli.

KNOWN ISSUE: test_context_sim_live still fails with status
'switching to: temp_livecontextsim' after a 60s wait. The click
appears to be re-triggering a project switch via the GUI's render
loop. Root cause investigation deferred; the sim is async and the
test path is fragile.

tests/test_extended_sims.py

@@ -22,12 +22,15 @@ def test_context_sim_live(live_gui: Any) -> None:
  sim = ContextSimulation(client)
  sim.setup("LiveContextSim")
  client.set_value('current_provider', 'gemini_cli')
+ # The gemini_cli adapter does not use the model name, but the controller's
+ # _do_generate path still reads it. Use an explicit placeholder so the
+ # downstream code does not raise KeyError on a stale 'model' field.
+ client.set_value('current_model', 'gemini-cli')
  client.set_value('gcli_path', f'"{sys.executable}" "{os.path.abspath("tests/mock_gemini_cli.py")}"')
  client.set_value('auto_add_history', True)
- sim.run() # Ensure history is updated via the async queue
+ sim.run()
  time.sleep(2)
  sim.teardown()
-
 @pytest.mark.integration
 def test_ai_settings_sim_live(live_gui: Any) -> None:
  """Run the AI Settings simulation against a live GUI."""