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] <[email protected]>

Author: dependabot[bot]

.github/workflows/claude.yml

@@ -26,7 +26,7 @@ jobs:
       id-token: write
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           fetch-depth: 1
 

.github/workflows/pages.yml

@@ -14,7 +14,7 @@ jobs:
       contents: write
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
 
       - name: Setup mdBook
         uses: peaceiris/actions-mdbook@v2

.github/workflows/release.yml

@@ -28,7 +28,7 @@ jobs:
       - name: Setup BuildX
         uses: docker/setup-buildx-action@v3
       - name: Checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           fetch-depth: 0
       - name: Get tags

.github/workflows/rust.yml

@@ -18,7 +18,7 @@ jobs:
     - name: Setup BuildX
       uses: docker/setup-buildx-action@v3
     - name: Checkout
-      uses: actions/checkout@v5
+      uses: actions/checkout@v6
       with:
         fetch-depth: 0
     - name: Get tags