Slim down CI runs per commit (#2911)

- Only run push-triggered workflows on main; PRs are covered by
  pull_request, so branch commits no longer run everything twice
- Test SQLite versions: single job, Python 3.13 + SQLite 3.25
- Fold coverage into the Python 3.14 test job (including serial
  tests) and remove test-coverage.yml; bump codecov-action to v5
- Cancel superseded in-progress runs on pull requests
- Prettier now also runs on pull requests

Claude-Session: https://claude.ai/code/session_012G7fa8HqJy9AkSjkocetAz

.github/workflows/test.yml

@@ -1,6 +1,15 @@
 name: Test
 
-on: [push, pull_request]
+on:
+  push:
+    branches:
+    - main
+  pull_request:
+  workflow_dispatch:
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: ${{ github.event_name == 'pull_request' }}
 
 permissions:
   contents: read
@@ -12,6 +21,9 @@ jobs:
       fail-fast: false
       matrix:
         python-version: ["3.10", "3.11", "3.12", "3.13", "3.14", "3.15"]
+        include:
+        - python-version: "3.14"
+          coverage: true
     steps:
     - uses: actions/checkout@v7
     - name: Set up Python ${{ matrix.python-version }}
@@ -29,12 +41,27 @@ jobs:
       run: |
         pip install . --group dev
         pip freeze
+    - name: Install pytest-cov
+      if: ${{ matrix.coverage }}
+      run: pip install pytest-cov
     - name: Run tests
       run: |
-        pytest -n auto -m "not serial"
-        pytest -m "serial"
+        if [ "${{ matrix.coverage }}" = "true" ]; then
+          COV="--cov=datasette --cov-config=.coveragerc"
+          pytest -n auto -m "not serial" $COV --cov-report=
+          pytest -m "serial" $COV --cov-append --cov-report xml:coverage.xml --cov-report term
+        else
+          pytest -n auto -m "not serial"
+          pytest -m "serial"
+        fi
         # And the test that exceeds a localhost HTTPS server
         tests/test_datasette_https_server.sh
+    - name: Upload coverage report
+      if: ${{ matrix.coverage }}
+      uses: codecov/codecov-action@v5
+      with:
+        token: ${{ secrets.CODECOV_TOKEN }}
+        files: coverage.xml
     - name: Black
       run: |
         black --version