Keep plugin.json version in sync with release tags

[jclusso]

Add a make release VERSION=x.y.z target that validates the version, rewrites the version field in .claude-plugin/plugin.json, commits, and tags v$(VERSION). It refuses to run on a dirty tree or with a non-semver version.

Add a verify-version job to the release workflow that gates GoReleaser: on a tag push it compares the tag against plugin.json and fails the release if they differ, so a forgotten bump can never ship.

Follow-up from PR #16.

[Copilot]

Pull request overview

Adds a make release VERSION=x.y.z workflow that bumps .claude-plugin/plugin.json, commits, and tags, plus a CI guard that fails the release workflow when the pushed tag and plugin.json version disagree. This closes the gap left by PR #16 where the plugin manifest version could drift from release tags.

Changes:

• New release target in Makefile that validates the version is semver, refuses to run on a dirty tree, rewrites plugin.json's version field, commits, and creates an annotated v$(VERSION) tag.
• New verify-version job in .github/workflows/release.yml that compares GITHUB_REF_NAME (stripped of leading v) to the version in plugin.json via jq, blocking GoReleaser via needs: on mismatch.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
Makefile	Adds release target: semver check, clean-tree check, in-place version rewrite, commit, and annotated tag.
.github/workflows/release.yml	Adds verify-version job gating goreleaser to enforce tag/manifest agreement on every release.

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