feat(2-A3b): requires_api_key enforcement in supervisor and GUI

- Add set_adapter_last_error method to ConfigStore for setting/clearing
  adapter error states
- Add API key precondition check in supervisor._start_adapter that:
  - Checks if adapter has requires_api_key attribute
  - Looks up the key via config_store.get_api_key
  - Sets last_error and returns early if key is missing
  - Clears last_error when adapter successfully starts
- Update adapters_list handler to compute api_key_missing flag
  for each adapter and pass to template
- Update adapters_edit_form handler to compute api_key_missing
  and requires_api_key_alias for template context
- Update adapters_list.html to show warning badge when api_key_missing
- Update adapters_edit.html to show warning article and disable
  Enable checkbox when api_key_missing
- Add tests for new functionality
- Fix test mocks to include requires_api_key and last_error fields

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

tests/test_supervisor_integration.py

@@ -94,6 +94,8 @@ class MockConfigSource:
 class MockNWSAdapter:
     """Mock NWSAdapter that tracks poll calls and allows control."""
 
+    requires_api_key = None  # Mock adapters don't require API keys
+
     def __init__(self, config, config_store, cursor_db_path) -> None:
         self.config = config
         self._config_store = config_store
@@ -152,6 +154,8 @@ def mock_config_store():
     store = MagicMock()
     store.list_streams = AsyncMock(return_value=[])
     store.get_stream = AsyncMock(return_value=None)
+    store.set_adapter_last_error = AsyncMock()
+    store.get_api_key = AsyncMock(return_value=None)
     return store