## Why
Archiving a thread can spike app-server CPU when the state DB does not
have a usable rollout path. The archive path falls back to locating the
rollout by thread id; because rollout filenames already contain the
UUID, the cheap fallback should find the file directly before invoking
broader file search.
## What Changed
- In `codex-rs/rollout/src/list.rs`, try the exact rollout filename
lookup before `codex-file-search`.
- Keep fuzzy search as the final legacy fallback when no filename match
is found.
- Preserve the legacy fallback when the filename scan hits a traversal
error, so an inaccessible stale subtree does not block lookup elsewhere.
## Verification
- `just test -p codex-rollout`
- `just test -p codex-thread-store`
- `just test -p codex-app-server thread_archive`
Eric TrautandGitHub
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