Speed up CI: uv installs, split pre-commit into mypy/pylint/rest

- pre-commit: drop the 28 s requirements.txt install (only
  dependency-freshness among the system hooks needs third-party code:
  pyyaml, packaging), run pre-commit directly instead of
  pre-commit/action, and split mypy and pylint into their own matrix
  jobs with per-group hook-env caches. Same hook set, same
  SKIP=free-days-interop (the rest group).
- Tests: uv with a cached wheel store for requirements.txt (pip took
  22 s), -q and -p no:sugar. No -n auto: the suite runs in ~0.5 s and
  measured ~1.2 s under pytest-xdist.
- free-days-interop (the critical path): build the freedays venv with
  uv instead of venv + pip (12 s).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0188kZdx3bb56QM8JFUnbHuM

.github/workflows/pre-commit.yml

@@ -7,8 +7,28 @@ on:
     branches: [main]
 
 jobs:
+  # mypy and pylint check the whole repo and are the two slowest hooks, so
+  # each gets its own runner and the other hooks share a third; the workflow
+  # takes as long as the slowest group rather than the sum.
   pre-commit:
     runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - group: mypy
+            hooks: mypy
+            skip: ""
+          - group: pylint
+            hooks: pylint
+            skip: ""
+          # free-days-interop needs Flutter and the freedays venv; it runs as
+          # its own job in python-tests.yml, so skipping it here is not
+          # fail-open.
+          - group: rest
+            hooks: ""
+            skip: mypy,pylint,free-days-interop
+    name: pre-commit (${{ matrix.group }})
     steps:
       - uses: actions/checkout@v4
 
@@ -27,10 +47,25 @@ jobs:
       - uses: actions/setup-python@v5
         with:
           python-version: "3.x"
-      - name: Install dependencies
-        run: pip install -r requirements.txt
-      # free-days-interop needs Flutter and the freedays venv; it runs as its
-      # own job in python-tests.yml, so skipping it here is not fail-open.
-      - uses: pre-commit/action@v3.0.1
+      - uses: astral-sh/setup-uv@v10.2.0
+
+      # Every hook brings its own environment except the language: system
+      # ones; of those only dependency-freshness imports third-party code
+      # (pyyaml, packaging). The whole requirements.txt used to be installed
+      # here for nothing -- 28 s of a 60 s run.
+      - name: Install pre-commit and the system hooks' imports
+        run: uv pip install --system pre-commit pyyaml packaging
+
+      # One cache per group: a shared key would hold whichever group saved
+      # first, and the others would rebuild their hook envs on every run. The
+      # restore key lets a config change reuse every env whose rev it kept.
+      - uses: actions/cache@v4
+        with:
+          path: ~/.cache/pre-commit
+          key: pre-commit-${{ matrix.group }}-${{ env.pythonLocation }}-${{ hashFiles('.pre-commit-config.yaml') }}
+          restore-keys: pre-commit-${{ matrix.group }}-${{ env.pythonLocation }}-
+
+      - name: pre-commit run (${{ matrix.group }})
         env:
-          SKIP: free-days-interop
+          SKIP: ${{ matrix.skip }}
+        run: pre-commit run ${{ matrix.hooks }} --all-files --show-diff-on-failure --color=always

.github/workflows/python-tests.yml

@@ -17,11 +17,22 @@ jobs:
         with:
           python-version: "3.x"
 
-      - name: Install dependencies
-        run: pip install -r requirements.txt
+      # uv with a cached wheel store (and cached builds of the three
+      # git+ kuhyx/utils packages) installs requirements.txt in seconds;
+      # plain pip took 22 s of a 32 s job.
+      - uses: astral-sh/setup-uv@v10.2.0
+        with:
+          enable-cache: true
+          cache-dependency-glob: requirements.txt
 
+      - name: Install dependencies
+        run: uv pip install --system -r requirements.txt
+
+      # No -n auto: the whole suite runs in ~0.5 s, and under pytest-xdist it
+      # measured ~1.2 s locally (worker start-up outweighs the parallelism).
+      # Coverage and its 100% bar come from pyproject.toml's addopts.
       - name: Run tests with coverage
-        run: python -m pytest -v
+        run: python -m pytest -q -p no:sugar
 
   # The Dart free-day rules are a port of ~/src/utils/freedays. This is the
   # cross-language gate (scripts/free_days_interop/check.sh): it needs both
@@ -42,11 +53,21 @@ jobs:
         with:
           python-version: "3.x"
 
+      # This job is the workflow's critical path (the Flutter SDK restore and
+      # the Dart test are its floor); uv builds the venv in a couple of
+      # seconds where venv + pip took 12 s.
+      - uses: astral-sh/setup-uv@v10.2.0
+        with:
+          enable-cache: true
+          cache-dependency-glob: |
+            .utils/crdt-sync/pyproject.toml
+            .utils/freedays/pyproject.toml
+
       - name: Install freedays into its own venv
         run: |
-          python -m venv .freedays-venv
-          .freedays-venv/bin/pip install --quiet .utils/crdt-sync
-          .freedays-venv/bin/pip install --quiet --no-deps .utils/freedays
+          uv venv --python "$pythonLocation/bin/python" .freedays-venv
+          uv pip install --quiet --python .freedays-venv/bin/python .utils/crdt-sync
+          uv pip install --quiet --python .freedays-venv/bin/python --no-deps .utils/freedays
 
       - uses: subosito/flutter-action@v2
         with: