After `deepseek fork` saves the forked session, surface the source
session title and the truncated source/new session ids so the user
sees what was created before the TUI takes over the screen.
Implementation differs slightly from the original PR:
- Reuse the existing `session_manager::truncate_id` helper instead of
defining a second copy in `main.rs`.
- Guard against an empty saved-title string so the line stays
readable for unnamed sessions.
This is a UX-only addition that does not address the broader
`/fork` request from #576; that one is asking for an in-TUI fork
picker, which is out of scope for v0.8.15.
Integrates #600.
Co-authored-by: macworkers <Mann_Juarezxgs@cash4u.com>
Hunter Bown
4eaeae91b5