uv hangs silently on the cache lock: -v names it, --no-cache bypasses

uv 0.13.6 guards UV_CACHE_DIR/.lock with flock: normal commands take it shared, uv cache clean takes it exclusive. While another process holds it exclusively, uv pip install and uv run print nothing and wait indefinitely (timed out after 8 s in a test). Rerun with -v: it prints 'INFO Waiting to acquire shared lock for <cache> at cache/.lock'. uv pip install --no-cache did not wait: it installed under the exclusive lock with rc 0. uv cache clean itself announces the wait ('Cache is currently in-use ... use --force to override'). Also: deleting an archive-v0 entry that no venv links to is safe; the next install re-prepares it under a new id.