CI: Use uv exclusively (#606)

## About
That's just maintenance. In this case, streamline the CI configuration
for improved ergonomics and future proofing, see GH-605.

## Details
- `activate-environment: true` of newer `astral-sh/setup-uv@v7` is the
killer feature here, which wasn't available before.
- Configuring `cache-dependency-glob: pyproject.toml` isn't needed,
because the recipe already employs an excellent default configuration
that includes this and other project metadata files.
- The adjustments in `test_cli` were needed because of a different PyPy
version installed by `setup-uv`. This will yield a report to Astral
maintainers, unrelated to this patch.

.github/workflows/docs.yaml

@@ -19,24 +19,16 @@ jobs:
   documentation:
     name: "Documentation"
     runs-on: ubuntu-latest
-    env:
-      UV_SYSTEM_PYTHON: true
 
     steps:
     - uses: actions/checkout@v4
 
-    - name: Set up Python
-      uses: actions/setup-python@v5
+    - name: Install uv
+      uses: astral-sh/setup-uv@v7
       with:
-        python-version: "3.13"
-
-    - name: Set up uv
-      uses: astral-sh/setup-uv@v5
-      with:
-        version: "latest"
+        activate-environment: true
         enable-cache: true
-        cache-dependency-glob: |
-          pyproject.toml
+        python-version: "3.14"
 
     - name: Install package and documentation dependencies
       run: uv pip install '.[docs]'

.github/workflows/test.yaml

@@ -28,8 +28,6 @@ jobs:
           "3.14t",
           "pypy3.11",
         ]
-    env:
-      UV_SYSTEM_PYTHON: true
 
     steps:
     - uses: actions/checkout@v4
@@ -37,19 +35,13 @@ jobs:
       with:
         node-version: 22
 
-    - name: Set up Python
-      uses: actions/setup-python@v5
+    - name: Install uv
+      uses: astral-sh/setup-uv@v7
       with:
-        python-version: ${{ matrix.python-version }}
-
-    - name: Set up uv
-      uses: astral-sh/setup-uv@v5
-      with:
-        version: "latest"
+        activate-environment: true
         enable-cache: true
         cache-suffix: ${{ matrix.python-version }}
-        cache-dependency-glob: |
-          pyproject.toml
+        python-version: ${{ matrix.python-version }}
 
     - name: Install package
       run: uv pip install '.[develop,test]'