- implement handling for unset ChatProvider selections
- add `iconUrl` attribute to ChatProvider object
- ensure icon and label synchronization when opening new windows or switching providers
- update tooltip l10nId string template to include `{ $provider } ({ $shortcut })`
- replace existing l10nId strings, sidebar-menu-open-ai-chatbot-tooltip
- use fluent strings for fallback
- fix ftl file: wrap shortcut in ()
- add property getter currentChatProviderInfo
- use lazy.chatProvider
- remove fallbackProvider10nId
- add new test_genai_chat_sidebar_tooltip test
Differential Revision: https://phabricator.services.mozilla.com/D231963