fix: downgrade actions/checkout from v6.0.1 to v4.2.2

Checkout v6.0.1 was released yesterday (Dec 2, 2025) and is causing CI
failures across all workflows. The v6 release requires minimum GitHub
Actions Runner v2.329.0 for Docker container scenarios and likely has
edge cases causing failures.

Downgrading to v4.2.2 (stable release from Oct 2024) to restore CI
stability. Can re-evaluate v6 after it matures.

Affects 16 checkout action references across 12 workflow files:
- quality-checks.yml
- waf-integration.yml
- docker-publish.yml
- codecov-upload.yml
- codeql.yml
- benchmark.yml
- docs.yml
- release-goreleaser.yml
- auto-versioning.yml
- docker-lint.yml
- auto-changelog.yml
- renovate.yml

.github/workflows/benchmark.yml

@@ -24,7 +24,7 @@ jobs:
     name: Performance Regression Check
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6
+      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
 
       - name: Set up Go
         uses: actions/setup-go@4dc6199c7b1a012772edbd06daecab0f50c9053c # v6