ci: simplify to single Linux/Python 3.12 job

Gitea only has Linux runners available. Drop the Python version matrix,
macOS/Windows jobs, and coverage artifact upload to reduce CI surface
area to what can actually run.

.gitea/workflows/ci.yml

@@ -7,21 +7,17 @@ on:
     branches: [main]
 
 jobs:
-  test-linux:
-    name: Tests (Linux, Python ${{ matrix.python-version }})
+  test:
+    name: Tests (Linux, Python 3.12)
     runs-on: ubuntu-latest
-    strategy:
-      fail-fast: false
-      matrix:
-        python-version: ["3.9", "3.11", "3.12"]
     steps:
       - name: Checkout
         uses: actions/checkout@v4
 
-      - name: Set up Python ${{ matrix.python-version }}
+      - name: Set up Python
         uses: actions/setup-python@v5
         with:
-          python-version: ${{ matrix.python-version }}
+          python-version: "3.12"
           cache: pip
           cache-dependency-path: |
             requirements.txt
@@ -42,54 +38,5 @@ jobs:
           python tagsync.py --help
           python tagsync.py status
 
-      - name: Run tests with coverage
-        run: |
-          pytest --cov=tagsync --cov-report=term-missing --cov-report=xml
-
-      - name: Upload coverage artifact
-        if: matrix.python-version == '3.12'
-        uses: actions/upload-artifact@v3
-        with:
-          name: coverage-xml
-          path: coverage.xml
-          retention-days: 14
-
-  test-macos:
-    name: Tests (macOS)
-    runs-on: macos-latest
-    # macOS runners are more expensive — only run on main-branch pushes
-    # and PRs that touch platform_macos.py or core logic.
-    if: github.event_name == 'push' || contains(github.event.pull_request.labels.*.name, 'platform')
-    steps:
-      - name: Checkout
-        uses: actions/checkout@v4
-
-      - name: Set up Python
-        uses: actions/setup-python@v5
-        with:
-          python-version: "3.12"
-
-      - name: Install dependencies
-        run: pip install -r requirements-dev.txt
-
       - name: Run tests
-        run: pytest -v
-
-  test-windows:
-    name: Tests (Windows)
-    runs-on: windows-latest
-    if: github.event_name == 'push' || contains(github.event.pull_request.labels.*.name, 'platform')
-    steps:
-      - name: Checkout
-        uses: actions/checkout@v4
-
-      - name: Set up Python
-        uses: actions/setup-python@v5
-        with:
-          python-version: "3.12"
-
-      - name: Install dependencies
-        run: pip install -r requirements-dev.txt
-
-      - name: Run tests
-        run: pytest -v
+        run: pytest