Add plugin sync check to CI (#36)

Validates that .claude-plugin/ and .cursor-plugin/ are in sync with
.plugin/plugin.json by running generate_plugin.py --check.

Author: anneschuth

.github/workflows/ci.yml

@@ -7,6 +7,20 @@ on:
     branches: [main]
 
 jobs:
+  validate-plugin:
+    name: Validate Plugin
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+    steps:
+      - uses: actions/checkout@v6
+
+      - name: Valideer plugin.json
+        run: python3 -c "import json; json.load(open('.plugin/plugin.json'))"
+
+      - name: Controleer plugin sync
+        run: python3 scripts/generate_plugin.py --check
+
   shellcheck:
     name: ShellCheck
     runs-on: ubuntu-latest