v0.0.6a2

Stop gating releases on a dated changelog entry (#480)

The changelog leg of the release gate could only be satisfied by the tagged
tree, so a missing or undated `## [X.Y.Z]` heading did not mean "write it up
before publishing" — it meant deleting the tag, committing a documentation
edit, and re-cutting the tag on the new commit. That is a bad trade for a file
a follow-up commit fixes, and it blocked both the PyPI publish and the docs
deploy on it.

What survives is the leg a tag genuinely can get wrong on its own: the shape.
uv-dynamic-versioning derives the distribution version from the tag, so a
`.postN`, `.devN`, local, or non-canonical (`-alpha1`) tag can never match the
version its own artifacts are built under, and is still refused before anything
builds. Writing up the release stays a release-checklist item in
`spec/process/production-readiness.md`, now marked as deliberately unenforced.