fix(#844): sync runtime manifest versions on npm version bump (#845)

* fix(#844): sync runtime manifest versions on npm version bump

The release workflow bumps package.json via `npm version` but never
stamped the runtime-integration manifests that must track it
(.claude-plugin/plugin.json #766, gemini-extension.json #775), so the
first RC/finalize whose version diverged from the -dev stream failed the
test suite before tagging/publishing.

Add scripts/sync-manifest-versions.cjs (single VERSIONED_MANIFESTS
registry) wired to a `version` npm lifecycle hook that stamps + stages
the manifests on every `npm version` — covering all four release bump
sites and local bumps with no workflow edits. A regression guard test
fails if any repo JSON whose version matches package.json is not
registered, forcing future version-bearing manifests into the sync.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* docs(#844): add changeset for manifest version sync fix

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

package.json

@@ -83,6 +83,7 @@
     "generate:identity": "node scripts/generate-package-identity.cjs",
     "prepack": "npm run build:lib",
     "prepare": "npm run build:lib",
+    "version": "node scripts/sync-manifest-versions.cjs --stage",
     "prepublishOnly": "npm run build:lib && npm run build:hooks",
     "pretest": "npm run build:lib && npm run lint:skill-deps",
     "pretest:coverage": "npm run build:lib && npm run lint:skill-deps",