feat: adopt changesets + fix exports, bump to 0.4.0

- Install @changesets/cli with fixed mode (all @uncaged/* packages sync version)
- Fix package exports: add bun condition, point import to dist/
- Bump all packages to 0.4.0 via changeset version
- Auto-generated CHANGELOG.md for each package
- Ignore workflow-dashboard (private)
- Add npm scripts: changeset, version, release
- publish.sh: support workspace:^ prefix matching

Closes #241, Closes #242

packages/workflow-util/package.json

@@ -14,7 +14,7 @@
     }
   },
   "dependencies": {
-    "@uncaged/workflow-protocol": "workspace:^"
+    "@uncaged/workflow-protocol": "workspace:*"
   },
   "devDependencies": {
     "typescript": "^5.8.3"