ci: validate config.example.yaml against config-schema.json (#627)

Extend the existing config-schema workflow to also validate
config.example.yaml against config-schema.json using check-jsonschema.

- add config.example.yaml to PR and push path triggers
- install check-jsonschema via pip
- run validation of config.example.yaml against schema

https://claude.ai/code/session_01Y1oqwE6mwNs9UTJgZRgXtG

---------

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

.github/workflows/config-schema.yml

@@ -4,11 +4,15 @@ on:
   pull_request:
     paths:
       - "config-schema.json"
+      - "config.example.yaml"
+      - ".github/workflows/config-schema.yml"
   push:
     branches:
       - main
     paths:
       - "config-schema.json"
+      - "config.example.yaml"
+      - ".github/workflows/config-schema.yml"
 
   workflow_dispatch:
 
@@ -39,3 +43,14 @@ jobs:
           fi
 
           echo "✓ config-schema.json is valid"
+
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: "3.x"
+
+      - name: Install check-jsonschema
+        run: pip install check-jsonschema
+
+      - name: Validate config.example.yaml against schema
+        run: check-jsonschema --schemafile config-schema.json config.example.yaml