When switching projects, the previous project's project-specific persona and
presets remained selected in the AI Settings panel because:
1. self.personas was not reloaded after switching project root
2. self.ui_active_persona / tool_preset / bias_profile / project_preset_name
were not validated against the newly-loaded personas/presets
Fix:
- Reload self.personas from self.persona_manager in _refresh_from_project
- Validate each active selection and reset to None/empty if it does not
exist in the newly-loaded manager dictionaries
- Push the active tool preset and bias profile to ai_client after the swap
- Initialize self.ui_active_bias_profile in class attribute block (was only
set later in __init__, causing AttributeError on direct attribute access)
Tests: 4 new tests in tests/test_project_switch_persona_preset.py verify
the reset behavior for persona, preset, tool preset, and global preset
preservation.
