## What changed
- Add `Environment::last_ready_info()` to return a snapshot of the most recently accepted `EnvironmentReadyInfo`.
- Preserve the distinction between no accepted report and an accepted report with no capability roots.
## Testing
- Cover pending, ordinary, failed, recovered, replaced, empty, and invalid readiness reports.
- Verify that previously returned snapshots remain unchanged after later reports.
GitOrigin-RevId: cd051a56e7ad54a673c851eb58238c5837335c03