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] <support@github.com>

Author: dependabot[bot]

.github/workflows/arm_mac_gcc.yml

@@ -9,7 +9,7 @@ jobs:
     name: ARM64 GCC
     runs-on: ubuntu-24.04-arm
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
 
     - name: Configure
       run: |

.github/workflows/codeql-analysis.yml

@@ -38,7 +38,7 @@ jobs:
 
     steps:
     - name: Checkout repository
-      uses: actions/checkout@v5
+      uses: actions/checkout@v6
 
     # Initializes the CodeQL tools for scanning.
     - name: Initialize CodeQL

.github/workflows/coverage.yml

@@ -18,7 +18,7 @@ jobs:
         std: ["11", "14", "17", "20"]
         unitBase: ["uint64_t", "uint32_t"]
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 0
 

.github/workflows/freebsd.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     name: run test on FreeBSD
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - name: Test in FreeBSD
       id: test
       uses: vmactions/freebsd-vm@v1

.github/workflows/pip.yml

@@ -15,7 +15,7 @@ jobs:
         python-version: ["3.12", "3.13"]
 
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
 
     - uses: actions/setup-python@v6
       with:
@@ -44,7 +44,7 @@ jobs:
         python-version: ["3.13"]
 
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
 
     - uses: actions/setup-python@v6
       with:
@@ -82,7 +82,7 @@ jobs:
         python-version: ["3.12", "3.13"]
 
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
 
     - uses: actions/setup-python@v6
       with:

.github/workflows/static-analyzers.yml

@@ -14,14 +14,14 @@ jobs:
     container: helics/buildenv:cpplint
 
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - name: Run cpplint
       run: cpplint --counting=detailed --recursive units test webserver converter  
   cppcheck:
     runs-on: ubuntu-latest
     container: helics/buildenv:cppcheck2
 
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
     - name: Run cppcheck
       run: cppcheck --enable=performance,portability --check-level=exhaustive --suppressions-list=config/cppcheck_suppressions.txt --error-exitcode=-4 -i ThirdParty -i FuzzTargets -i docs -i config .

.github/workflows/tests.yml

@@ -13,7 +13,7 @@ jobs:
     name: CMake config check 3.7-3.11
     runs-on: ubuntu-22.04
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
 
     - name: update certificates
       run: |
@@ -58,7 +58,7 @@ jobs:
     name: CMake config check 3.12+
     runs-on: ubuntu-24.04
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
 
     - name: Check CMake 3.12
       uses: ./.github/actions/quick_cmake

.github/workflows/wheels.yml

@@ -13,7 +13,7 @@ jobs:
     name: Build SDist
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
       with:
         submodules: true
 
@@ -38,7 +38,7 @@ jobs:
         os: [ubuntu-latest, ubuntu-24.04-arm, macos-14, windows-latest]
 
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
       with:
         submodules: true