ci: pin GitHub Actions by SHA instead of mutable tags (staging sync)

Cherry-pick from main (03689e3d) to restore SHA pinning on staging branch.

- actions/checkout@v6 → @de0fac2e4500dabe0009e67214ff5f5447ce83dd (v6.0.2)
  in .github/workflows/secret-pattern-drift.yml
- pypa/gh-action-pypi-publish@release/v1 →
  @cef221092ed1bacb1cc03d23a2d87d1d172e277b in .github/workflows/publish-runtime.yml

Mutable action tags create supply-chain risk. SHA-pinning ensures the exact
commit runs every time.

[core-devops-agent]

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

.github/workflows/publish-runtime.yml

@@ -180,7 +180,7 @@ jobs:
         # environment pypi-publish. The action mints a short-lived OIDC
         # token and exchanges it for a PyPI upload credential — no static
         # API token in this repo's secrets.
-        uses: pypa/gh-action-pypi-publish@release/v1
+        uses: pypa/gh-action-pypi-publish@cef221092ed1bacb1cc03d23a2d87d1d172e277b # release/v1
         with:
           packages-dir: ${{ runner.temp }}/runtime-build/dist/
 

.github/workflows/secret-pattern-drift.yml

@@ -48,7 +48,7 @@ jobs:
     runs-on: ubuntu-latest
     timeout-minutes: 5
     steps:
-      - uses: actions/checkout@v6
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
 
       - uses: actions/setup-python@a309ff8b426b58ec0e2a45f0f869d46889d02405 # v6.2.0
         with: