## Why
Native clipboard setup and writes can block, preventing the TUI from processing input or closing overlays while a copy is in progress.
## What changed
- Route clipboard copies through one session worker that retains native clipboard ownership. Keep terminal escape output on the UI thread.
- Show pending and busy status messages, reject additional copies without queuing them, and ask users to retry image paste after an active copy finishes.
- Abandon setup after five seconds and prevent late delivery. Keep the worker busy until the blocked call returns, and bound shutdown waiting for clipboard handoff.
- Match completions to their originating requests so stale results cannot clear newer selections or unexpectedly resume transcript following. Retain selections on automatic copies, failures, and unconfirmed delivery.
## Testing
Add regression tests for blocked backends, overlay exit, copy and paste ordering, setup expiry, bounded shutdown, completion status messages, and preservation of replaced or moved selections.
GitOrigin-RevId: 4ba1f8da258b9d0700b0edec9ac0ba699f536785
Felipe Coury
12fd929f72