Use the shared release-signing actions from astral-sh/github-actions#3
at a fixed commit for planning, preparation, signing, notarization,
assembly, and native verification. `uv` declares the `uv` and `uv_build`
executable inventories, while the shared planner discovers the
applicable `cargo-dist` targets and assigns their native verification
runners. Remove the duplicate local planning, signing, and packaging
scripts.
`uv` still assembles the complete release, including unsigned targets
and source distributions, and owns release approval, artifact transfers,
wheel-content checks, smoke tests, and publication. This supersedes
#21552 and should follow the shared-actions pull request.
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Co-authored-by: Zanie Blue <contact@zanie.dev>
