Bump actions/checkout from 4 to 6

Bumps [actions/checkout](https://github.com/actions/checkout) from 4 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v4...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/lint.yml

@@ -16,7 +16,7 @@ jobs:
         python-version: [ '3.13' ]
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - name: Set up Python
         uses: actions/setup-python@v5
         with:
@@ -38,7 +38,7 @@ jobs:
         python-version: [ '3.9', '3.13' ]
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - name: Set up Python
         uses: actions/setup-python@v5
         with:

.github/workflows/python-package.yml

@@ -41,7 +41,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     timeout-minutes: 30
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
         with:
           ref: ${{ github.event.pull_request.head.sha }}
       - name: Set up Python ${{ matrix.python-version }}
@@ -67,7 +67,7 @@ jobs:
   build-sdist:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - name: Set up Python
         uses: actions/setup-python@v5
         with:

.github/workflows/release.yml

@@ -12,7 +12,7 @@ jobs:
     name: Test gate (must pass before publish)
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - name: Set up Python
         uses: actions/setup-python@v5
         with:
@@ -41,7 +41,7 @@ jobs:
         arch: [ auto, aarch64 ]
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Set up QEMU
         if: ${{ matrix.arch == 'aarch64' }}
@@ -87,7 +87,7 @@ jobs:
         os: [ macos-latest, windows-latest ]
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Set up Python
         uses: actions/setup-python@v5
@@ -136,7 +136,7 @@ jobs:
     needs: test-gate
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - name: Set up Python
         uses: actions/setup-python@v5
         with:

.github/workflows/wheels.yml

@@ -24,7 +24,7 @@ jobs:
         arch: [ auto, aarch64 ]
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - name: Set up QEMU
         if: ${{ matrix.arch == 'aarch64' }}
         uses: docker/setup-qemu-action@v4
@@ -59,7 +59,7 @@ jobs:
         os: [ macos-latest, windows-latest ]
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - name: Set up Python
         uses: actions/setup-python@v5
         with: