ci: 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/ai-enhancement-guide.yml

@@ -21,7 +21,7 @@ jobs:
       || (github.event.action == 'labeled' && github.event.label.name == 'enhancement')
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 1
 

.github/workflows/ai-review.yml

@@ -12,7 +12,7 @@ jobs:
   review:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
         with:
           # Checkout base repo (not PR head) for safe access to CLAUDE.md and proposals.
           # The diff is fetched via GitHub API, not from the PR code.

.github/workflows/daily-digest.yml

@@ -12,7 +12,7 @@ jobs:
   digest:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 0  # Full history for git log
 

.github/workflows/docs.yml

@@ -25,7 +25,7 @@ jobs:
   build:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Install mdBook
         run: |

.github/workflows/nightly.yml

@@ -18,7 +18,7 @@ jobs:
       fail-fast: false
     name: test (Mendix ${{ matrix.mendix-version }})
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
 
       - uses: actions/setup-go@v6
         with:
@@ -41,7 +41,7 @@ jobs:
     needs: test
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 0
 

.github/workflows/push-test.yml

@@ -9,7 +9,7 @@ jobs:
   build-and-test:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: actions/setup-go@v6
         with:
           go-version: '1.26'

.github/workflows/release.yml

@@ -12,7 +12,7 @@ jobs:
   release:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 0
       - uses: actions/setup-go@v6