ci: Validate problems.yaml against the schema on every pull request

The old New Problem Check workflow only ran when triggered manually and
used utils/validate_yaml.py, which still expects the old list-based format
and fails on the current problems.yaml. Replace it with a check that runs
opl validate on every pull request and push to main.

Author: olafmersmann

.github/workflows/new_problem_check.yml

@@ -15,17 +15,13 @@ jobs:
       - name: Checkout repository
         uses: actions/checkout@v7
 
-      - name: Set up Python
-        uses: actions/setup-python@v6
+      - name: Install uv
+        uses: astral-sh/setup-uv@v10.3.2
         with:
-          python-version: '3.x'
+          python-version: 3.14
 
       - name: Install dependencies
-        run: |
-          python -m pip install --upgrade pip
-          pip install -r utils/requirements.txt
+        run: uv sync --dev
 
       - name: Run New Problem Check
-        run: |
-          uv run utils/validate_yaml.py problems.yaml
-
+        run: uv run utils/validate_yaml.py problems.yaml

.github/workflows/validate_problems.yml

@@ -0,0 +1,30 @@
+name: Validate problems.yaml
+
+on:
+  push:
+    branches: ["main"]
+  pull_request:
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+jobs:
+  validate:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v6
+        with:
+          persist-credentials: false
+
+      - name: Install uv
+        uses: astral-sh/setup-uv@v7
+        with:
+          python-version: "3.10"
+
+      - name: Install the project
+        run: uv sync
+
+      - name: Validate problems.yaml against the schema
+        run: uv run opl validate problems.yaml