Bump actions/checkout from 5 to 6

Bumps [actions/checkout](https://github.com/actions/checkout) from 5 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v5...v6)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

.github/workflows/build.yml

@@ -16,7 +16,7 @@ jobs:
       matrix:
         python-version: ['3.10', '3.11', '3.12', '3.13', '3.14']
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - uses: astral-sh/setup-uv@v7
     - run: make check
     - run: uv run coverage xml
@@ -27,13 +27,13 @@ jobs:
   lint:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - uses: astral-sh/setup-uv@v7
     - run: make lint
 
   docs:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - uses: astral-sh/setup-uv@v7
     - run: make html

.github/workflows/codspeed.yml

@@ -11,7 +11,7 @@ jobs:
   benchmarks:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - uses: astral-sh/setup-uv@v7
     - uses: CodSpeedHQ/action@v4
       with:

.github/workflows/release.yml

@@ -9,7 +9,7 @@ jobs:
     runs-on: ubuntu-latest
     permissions: write-all
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - uses: astral-sh/setup-uv@v7
     - run: uv build
     - run: uv run -w . mkdocs gh-deploy --force