release: v0.1.0

First cut release. Snapshots ./src/ as ./versions/v0.1.0/ via
`just cut-version v0.1.0` (22 files: 21 chapter MDs + SUMMARY.md).
Deployed alongside `latest` at:

  https://swaits.github.io/meshcore-spec/v0.1.0/

Also:

- CHANGELOG.md adopts Keep a Changelog-style version sections.
  Future entries land under [Unreleased] and graduate to a version
  heading when cut. The existing date-stamped pass entries stay
  put as a historical record of the work captured in v0.1.0.
- README.md fixes a stale "per vX.Y.Z tag" mention left over from
  the tag-based versioning model, and links the current release
  explicitly.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

README.md

@@ -4,8 +4,9 @@ A comprehensive specification and conformance test suite for the
 [MeshCore](https://github.com/meshcore-dev/MeshCore) mesh networking protocol.
 
 **📖 Read the spec online:** <https://swaits.github.io/meshcore-spec/>
-(rolling `latest` build, plus a frozen snapshot per `vX.Y.Z` tag — pick one
-from the version-picker in the top-right of any page)
+(rolling `latest` from `main`, plus a frozen snapshot per release —
+current: [v0.1.0](https://swaits.github.io/meshcore-spec/v0.1.0/). Use
+the version-picker in the top-right of any page to switch.)
 
 MeshCore Spec aims to be the authoritative, machine-readable definition of the
 MeshCore wire format — much like [RubySpec](https://github.com/ruby/spec) became