Allow users to create Gemini provider configurations without API key
and fill it in later. Split validation into two modes:
- validate_gemini_settings: Basic structure check (used when adding)
- validate_gemini_settings_strict: Full validation (used when switching)
This fixes the error 'Gemini config missing required field: GEMINI_API_KEY'
when trying to add Gemini providers from presets like PackyCode or Google.
Changes:
- Add validate_gemini_settings_strict for switching validation
- Update write_gemini_live to use strict validation
- Add comprehensive tests for both validation modes
Refactor tray menu system to support three applications (Claude/Codex/Gemini):
- Introduce generic TrayAppSection structure and TRAY_SECTIONS array
- Implement append_provider_section and handle_provider_tray_event helper functions
- Enhance Gemini provider service with .env config read/write support
- Implement Gemini LiveSnapshot for atomic operations and rollback
- Update README documentation to reflect Gemini tray quick switching feature