chore(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)
- [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/evals-nightly.yml

@@ -29,7 +29,7 @@ jobs:
 
     steps:
       - name: 'Checkout code'
-        uses: 'actions/checkout@v4' # ratchet:exclude
+        uses: 'actions/checkout@v6' # ratchet:exclude
 
       - name: 'Set up Node.js'
         uses: 'actions/setup-node@v4' # ratchet:exclude

.github/workflows/gemini-issue-fixer.yml

@@ -36,7 +36,7 @@ jobs:
           permission-pull-requests: 'write'
 
       - name: 'Checkout repository'
-        uses: 'actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8' # ratchet:actions/checkout@v6
+        uses: 'actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5' # ratchet:actions/checkout@v6
 
       - name: 'Run Gemini PR Create'
         uses: 'google-github-actions/run-gemini-cli@main' # ratchet:exclude

.github/workflows/gemini-review.yml

@@ -39,7 +39,7 @@ jobs:
           permission-pull-requests: 'write'
 
       - name: 'Checkout repository'
-        uses: 'actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8' # ratchet:actions/checkout@v6
+        uses: 'actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5' # ratchet:actions/checkout@v6
 
       - name: 'Run Gemini pull request review'
         uses: 'google-github-actions/run-gemini-cli@main' # ratchet:exclude

.github/workflows/publish.yml

@@ -16,7 +16,7 @@ jobs:
 
     steps:
       - name: 'Checkout'
-        uses: 'actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8' # ratchet:actions/checkout@v6
+        uses: 'actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5' # ratchet:actions/checkout@v6
 
       - name: 'Publish'
         id: 'publish'