Function current_commit_sha 

pub async fn current_commit_sha(root: &Path) -> String

The current commit’s SHA, with "unknown" on any failure.

Deliberately lossy: this is the cache-key component for repeated LLM calls, and a cache-key component must never take analysis down. A hung git is a real failure mode in CI containers; the 5s timeout plus the “unknown” fallback means the worst case is a cache miss, not a gate stall.