Un-slim the bundle's uv cache: prune_uv_cache_to_built (built-only keep-set)
is deleted — every wheel the build resolved ships, so any per-install venv
rebuild (plugin extras, feature changes) resolves offline with zero network.
stage_uv_cache keeps excluding sdist src/ trees (build-only bulk) but now
KEEPS built wheel ZIPs including the copies beside sdist metadata.msgpack
shards: probing showed an offline rebuild whose revision entry lacks its
wheel ZIP fails closed wanting the sdist download. Fixture sdist uses a
stdlib-only PEP 517 backend so the hermetic offline rebuild needs no build
tools.
4f3b8d713e