Greptile Summary

This PR fixes offline mode for remote version resolution by (1) making list_remote_versions_with_info read the on-disk remote_versions.msgpack.z cache instead of returning an empty list when offline, and (2) centralising the latest_stable_version → list fallback in Backend::latest_version so every backend benefits without duplicating the fallback logic.

The previously-flagged issues (in-memory OnceCell check, default latest_stable_version returning Ok(None), and the redundant double-call) are all addressed in the current head commit.

Confidence Score: 5/5

Safe to merge — all previously flagged concerns are addressed and the new tests validate the offline cache path end-to-end.

All remaining findings are P2 or below. The core logic is correct, the centralised fallback removes duplication, and get_cached() correctly prefers in-memory state before hitting disk. The four new unit tests directly exercise the fixed code paths.

No files require special attention.

Important Files Changed

Sequence Diagram

sequenceDiagram
    participant CLI
    participant Backend
    participant Cache as CacheManager

    Note over CLI,Cache: Offline latest resolution (after this PR)

    CLI->>Backend: latest_version(None, None)
    Backend->>Backend: latest_stable_version()
    alt fast path returns Some(version)
        Backend-->>CLI: Ok(Some(version))
    else fast path returns Ok(None)
        Backend->>Backend: latest_version_for_query("latest", None)
        Backend->>Backend: list_remote_versions_with_info()
        Backend->>Cache: get_cached()
        alt in-memory hit (cache_async / cache)
            Cache-->>Backend: Ok(versions)
        else disk read
            Cache->>Cache: parse() → read msgpack.z
            Cache-->>Backend: Ok(versions) or Err
        end
        alt versions found
            Backend-->>CLI: Ok(Some(latest))
        else no cache
            Backend-->>CLI: Ok(vec![]) → Ok(None)
        end
    end

_{Reviews (2): Last reviewed commit: "fix(backend): use remote version cache o..." | Re-trigger Greptile}