## What changed
- Add `StartThreadOptions::new` to provide the standard configuration for a new thread.
- Make `ThreadManager::start_thread` the single thread-start entry point and migrate callers from the previous convenience methods.
- Derive default environment selections when `environments` is `None`, while preserving explicit selections, including an empty list.
GitOrigin-RevId: 8977dc11aed54c5e1215a81eaed2b2cf5fc6087a
## Why
Startup prewarms and Guardian review sessions do not need workspace Git metadata. Collecting it for those requests performs redundant work, while user turns still need a fresh view of the repository.
## What changed
- Add a per-session Git enrichment policy.
- Skip enrichment for startup prewarm, preview, and Guardian review turns.
- Keep fresh enrichment enabled for regular sessions and one-shot delegated turns.
## Testing
- Cover prewarm and Guardian requests omitting workspace metadata while subsequent user turns observe repository changes.
- Cover concurrent repositories and worktrees retaining distinct metadata.
- Verify concurrent enrichment is coalesced and canceled enrichment can be retried.
GitOrigin-RevId: 4a68615288bb568c75f2e487d9c0776e3e80f191
pakrym-oai