Deduplicate all files in the wheel cache - #21327
Summary
This PR adds file-level deduplication to uv's wheel cache by storing each file under its hash in a files-v0 bucket and hardlinking into archive-v0. It aims to reduce cache footprint and enable cleanup, trading minor slowdowns for cold installs against larger efficiency gains. Benchmarks show cache savings and discuss follow-up optimizations such as buffer reuse.