feat: tag and publish a Gitea release on every push to master

Replicate the dsh-facet release stack: a Gitea Actions workflow
(.gitea/workflows/release.yml) + .gitea/scripts/release.sh read the commit
subjects since the last tag, bump package.json, prepend CHANGELOG.md, tag
vX.Y.Z and publish the release via API. Agreed install ref is
#semver:^0.1.0, and tags are what 'dsh plugin --profile web update' moves
to, so the workflow is what makes updates work. Add the release.test.sh
suite (43 checks), npm scripts (test:release / release:plan /
release:notes), AGENTS.md with the commit conventions, CHANGELOG.md seed,
and the README *Releases* rules.

package.json

@@ -1,12 +1,18 @@
 {
   "name": "dsh-browser-install",
   "version": "0.1.0",
+  "private": true,
   "description": "Auto-installs Playwright Chromium (npx playwright install chromium --with-deps) into the DSH container and bridges it onto PATH so dsh-ego-browser finds it without manual env-var or wrapper steps.",
   "type": "module",
   "main": "index.js",
   "license": "MIT",
   "engines": {
-    "node": ">=22"
+    "node": ">=22.5"
+  },
+  "scripts": {
+    "test:release": "bash .gitea/scripts/release.test.sh",
+    "release:plan": "bash .gitea/scripts/release.sh should-release \"$(bash .gitea/scripts/release.sh range)\"",
+    "release:notes": "bash .gitea/scripts/release.sh notes \"$(bash .gitea/scripts/release.sh range)\""
   },
   "dependencies": {
     "@deepseek-ai/schemastery": "^3.18.3"