Add pull request draft generation to the commit_ai crate and expose it
via a new Tauri command. The backend builds a branch-range context from
published remote-tracking refs only, calls the chosen AI provider, and
parses a JSON {"title","description"} draft (with validation). Also
register the command in the app and add unit tests for parsing and the
branch-context behavior.
Consolidate AI settings in the frontend by renaming the dialog to an
AiSettingsPage and integrating AI options into the main AppSettings
dialog. Persisted AI preferences are merged with existing localStorage
rather than replacing it, and the settings UI now supports opening the
app settings to a specific initial page ("integrations" or "ai").
Other changes:
- Replace the commit-message system prompt used by build_messages with
the updated, more detailed guidance text.
Christoph
4b5de5a88b