Function wait_for 

pub async fn wait_for(
    home: &Path,
    cache_dir: &Path,
    owner: &Owner,
    budget: Duration,
    poll: Duration,
) -> Result<Guard>

Acquire the lease for cache_dir, waiting out contention rather than failing on the first busy owner — but never past budget, and the wait comes out of that same budget rather than a second, unbounded one. A caller already has a node timeout; this is that timeout, not a new clock next to it, which is what keeps a wait from becoming the “無期限待機” AGENTS.md’s own build-cache section warns is never acceptable. The error on timeout names who is still holding it, for the event this gets logged into.