## What changed
- Fetch `collaborationMode/list` during TUI startup and reconnect, and use the
returned catalog for visible collaboration-mode selection.
- Keep collaboration-mode discovery optional with a two-second timeout so an
unavailable, invalid, or unsupported response does not block bootstrap.
- Preserve discovered modes when the model catalog refreshes, clear restored
developer-instruction overrides when selecting a server mode, and retain a
`/plan` draft when plan mode is unavailable.
## Testing
- Cover optional discovery failures and catalog refresh on reconnect.
- Cover server mode selection, model refreshes, restored settings, and
unavailable plan mode.
GitOrigin-RevId: a6e35c14aab2e38526606164091ac64c500151bb