## Why
The thread inventory check compared state database rows only with plain
`.jsonl` rollout files. Once a rollout was compressed to `.jsonl.zst`, the
check could report its canonical database row as stale and omit the rollout
from parity results.
## What changed
- Scan completed compressed rollouts and match them to database rows using
their canonical `.jsonl` paths.
- Prefer a plain rollout when both plain and compressed siblings exist, and
ignore compression temporary files.
- Keep unreadable compressed rollouts in the set of existing paths so they
produce scan errors without also producing misleading stale-row reports.
- Use canonical paths when deriving legacy thread IDs and archived status.
## Testing
Added coverage for active and archived compressed rollouts, plain/compressed
siblings, metadata and legacy filename IDs, corrupt compressed data, and
compression temporary files.
GitOrigin-RevId: 2461376432194a4062beedbe875aa7002dd2049f
b8b61bc692