cowork-bot: pin actions/checkout to v4.2.2 SHA (security hardening)

Author: DevForge Engineer

.github/workflows/publish.yml

@@ -23,7 +23,7 @@ jobs:
     environment: pypi
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5  # v4.2.2 (pinned)
         with:
           persist-credentials: false
 
@@ -62,7 +62,7 @@ jobs:
       contents: read
       id-token: write
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5  # v4.2.2 (pinned)
         with:
           persist-credentials: false
       - uses: actions/setup-node@v4