docs: remove version numbers from README

[bntvllnt]

Removes distribution version numbers from the README, so routine version bumps don't need a README edit.

• The README points to VERSION, CHANGELOG.md, and the GitHub releases page instead.
• Historical evidence is still identified by commit SHA.
• The updater's -dev.N/-canary.N suffix rule is kept, since it describes the versioning scheme rather than a version to update.
• CHANGELOG keeps its versioned history, because that is its purpose.

Checks: 37 tests OK; sync.py --check no drift; git diff --check clean.

https://claude.ai/code/session_01QibzbuYP9NMPNKJdURfxfE