## Why
Threads need a visible title while automatic generation is pending or fails. Hidden title-generation requests must also stay out of the foreground conversation, including during skill installation prompts.
## What changed
- Immediately display a Markdown-stripped, single-line excerpt of the first message, capped at 60 characters. Replace it with the generated title, or save the excerpt if generation fails or returns an invalid title.
- Give title threads explicit read-only permissions and request the `never` approval policy, subject to managed policy constraints. Keep blocking input requests on the hidden thread until timeout.
- Interrupt timed-out temporary structured turns before detaching them.
## Testing
Add coverage for provisional title replacement, fallback persistence, managed permission and approval policies, and hidden input requests. Add a terminal integration test that verifies title generation after choosing “Continue anyway” on a skill installation prompt.
GitOrigin-RevId: f408f3061e5e7f0d9d6bc1f2f9674303e9e68400
