fix: Pin all GitHub Actions to full commit SHAs (13 files)

Security compliance - SHA pinning for all actions.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

.github/workflows/autonomous-cross-repo.yml

@@ -51,7 +51,7 @@ jobs:
       sync_files: ${{ steps.changes.outputs.files }}
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683
         with:
           fetch-depth: 2
 
@@ -105,12 +105,12 @@ jobs:
 
     steps:
       - name: Checkout Source
-        uses: actions/checkout@v4
+        uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683
         with:
           path: source
 
       - name: Checkout Target
-        uses: actions/checkout@v4
+        uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683
         with:
           repository: ${{ matrix.repo }}
           path: target
@@ -195,12 +195,12 @@ jobs:
 
     steps:
       - name: Checkout Source
-        uses: actions/checkout@v4
+        uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683
         with:
           path: source
 
       - name: Checkout Target
-        uses: actions/checkout@v4
+        uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683
         with:
           repository: ${{ matrix.repo }}
           path: target
@@ -266,7 +266,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683
 
       - name: Analyze Dependencies
         id: deps