ci: single-source Python version via pyproject.toml + add uv-lock pre-commit hook (#15111)

- Add astral-sh/uv-pre-commit (uv-lock) so uv.lock stays in sync with
  pyproject.toml automatically instead of relying on manual relocks.
- Replace 'python-version: 3.14' with 'python-version-file: pyproject.toml'
  in every workflow that uses actions/setup-python (build, project_euler,
  sphinx, directory_writer), making requires-python the single source of
  truth for the interpreter version.

.github/workflows/build.yml

@@ -17,7 +17,7 @@ jobs:
           cache-dependency-glob: uv.lock
       - uses: actions/setup-python@v7
         with:
-          python-version: 3.14
+          python-version-file: pyproject.toml
           allow-prereleases: true
       - run: uv sync --group=test
       - name: Run tests

.github/workflows/directory_writer.yml

@@ -11,7 +11,7 @@ jobs:
           fetch-depth: 0
       - uses: actions/setup-python@v7
         with:
-          python-version: 3.14
+          python-version-file: pyproject.toml
           allow-prereleases: true
       - name: Write DIRECTORY.md
         run: |

.github/workflows/project_euler.yml

@@ -25,7 +25,7 @@ jobs:
       - uses: astral-sh/setup-uv@v7
       - uses: actions/setup-python@v7
         with:
-          python-version: 3.14
+          python-version-file: pyproject.toml
           allow-prereleases: true
       - run: uv sync --group=euler-validate --group=test
       - run: uv run pytest --doctest-modules --cov-report=term-missing:skip-covered --cov=project_euler/ project_euler/
@@ -43,7 +43,7 @@ jobs:
       - uses: astral-sh/setup-uv@v7
       - uses: actions/setup-python@v7
         with:
-          python-version: 3.14
+          python-version-file: pyproject.toml
           allow-prereleases: true
       - run: uv sync --group=euler-validate --group=test
       - run: uv run pytest scripts/validate_solutions.py

.github/workflows/sphinx.yml

@@ -36,7 +36,7 @@ jobs:
       - uses: astral-sh/setup-uv@v7
       - uses: actions/setup-python@v7
         with:
-          python-version: 3.14
+          python-version-file: pyproject.toml
           allow-prereleases: true
       - run: uv sync --group=docs
       - uses: actions/configure-pages@v6

.pre-commit-config.yaml

@@ -18,6 +18,11 @@ repos:
     hooks:
       - id: auto-walrus
 
+  - repo: https://github.com/astral-sh/uv-pre-commit
+    rev: 0.12.7
+    hooks:
+      - id: uv-lock
+
   - repo: https://github.com/astral-sh/ruff-pre-commit
     rev: v0.16.1
     hooks: