Update actions/checkout action to v6 (#825)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

.github/workflows/codeql-analysis.yml

@@ -36,7 +36,7 @@ jobs:
 
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       # Initializes the CodeQL tools for scanning.
       - name: Initialize CodeQL

.github/workflows/merge.yml

@@ -26,7 +26,7 @@ jobs:
     if: github.event.pull_request.merged == true
     steps:
       - name: Check out committed code
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Prepare uv
         run: |
           pip install uv

.github/workflows/verify.yml

@@ -26,7 +26,7 @@ jobs:
       python-version: ${{ steps.python.outputs.python-version }}  # Ensure all runners use THIS minor version
     steps:
       - name: Check out committed code
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Set up Python and determine minor version for ${{ env.DEFAULT_PYTHON }}
         id: python
         uses: actions/setup-python@v6
@@ -63,7 +63,7 @@ jobs:
       - prepare
     steps:
       - name: Check out committed code
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           persist-credentials: false
       - name: Restore cached environment
@@ -101,7 +101,7 @@ jobs:
       - dependencies_check
     steps:
       - name: Check out committed code
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Restore cached environment
         id: cache-reuse
         uses: plugwise/gh-actions/restore-venv@v1
@@ -136,7 +136,7 @@ jobs:
         python-version: ["3.14", "3.13"]
     steps:
       - name: Check out committed code
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Set up Python ${{ matrix.python-version }}
         id: python
         uses: actions/setup-python@v6
@@ -172,7 +172,7 @@ jobs:
       - pytest
     steps:
       - name: Check out committed code
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           persist-credentials: false
       - name: Restore cached environment
@@ -195,7 +195,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Check out committed code
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Run ShellCheck
         uses: ludeeus/action-shellcheck@master
 
@@ -205,7 +205,7 @@ jobs:
     name: Dependency
     steps:
       - name: Check out committed code
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Run dependency checker
         run: scripts/dependencies_check.sh debug
 
@@ -219,7 +219,7 @@ jobs:
       - mypy
     steps:
       - name: Check out committed code
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Restore cached environment
         id: cache-reuse
         uses: plugwise/gh-actions/restore-venv@v1
@@ -259,7 +259,7 @@ jobs:
       - mypy
     steps:
       - name: Check out committed code
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Prepare uv
         run: |
           pip install uv
@@ -301,7 +301,7 @@ jobs:
       - coverage
     steps:
       - name: Check out committed code
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Restore cached environment
         id: cache-reuse
         uses: plugwise/gh-actions/restore-venv@v1