The prune option uninstalled all managed Python versions (and tools)
and reinstalled them on every activation, which is slow. Instead,
resolve each requested version to the install target uv would produce
and uninstall only the difference; already-correct versions are left
untouched. Resolving to the install target (not every installed match)
also prunes superseded patch releases, which uv retains on upgrade.
Tools are diffed by PEP 503-normalized package name: requested names
are extracted and normalized at build time, and the installed set is
read from uv's tool directory, whose entries are already normalized, so
no uv output is parsed. Pruning to an empty set still removes everything.
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