build(deps): 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] <[email protected]>

Author: dependabot[bot]

.github/workflows/claude.yml

@@ -26,7 +26,7 @@ jobs:
       actions: read # Required for Claude to read CI results on PRs
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           fetch-depth: 1
 

.github/workflows/dependabot-dedupe.yml

@@ -14,7 +14,7 @@ jobs:
     if: ${{ github.actor == 'dependabot[bot]' }}
     steps:
       - name: Check out repo
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           ref: ${{ github.head_ref }}
           fetch-depth: 0

.github/workflows/main.yml

@@ -14,7 +14,7 @@ jobs:
     name: Check workflows
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - name: Download actionlint
         id: download-actionlint
         run: bash <(curl https://raw.githubusercontent.com/rhysd/actionlint/7fdc9630cc360ea1a469eed64ac6d78caeda1234/scripts/download-actionlint.bash) 1.6.25

.github/workflows/publish-preview.yml

@@ -12,7 +12,7 @@ jobs:
     outputs:
       IS_FORK: ${{ steps.is-fork.outputs.IS_FORK }}
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - name: Determine whether this PR is from a fork
         id: is-fork
         run: echo "IS_FORK=$(gh pr view --json isCrossRepository --jq '.isCrossRepository' "${PR_NUMBER}" )" >> "$GITHUB_OUTPUT"
@@ -29,7 +29,7 @@ jobs:
     if: ${{ needs.is-fork-pull-request.outputs.IS_FORK == 'false' }}
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - name: Check out pull request
         run: gh pr checkout "${PR_NUMBER}"
         env: