ci: pin GitHub Actions to commit SHAs

Pin all GitHub Actions referenced in generated workflows (both
first-party `actions/*` and third-party) to immutable commit SHAs.
Updating pinned actions is now a deliberate codegen-side bump rather
than implicit on every workflow run.

Author: stainless-app[bot]

.github/workflows/ci.yml

@@ -21,7 +21,7 @@ jobs:
     runs-on: ${{ github.repository == 'stainless-sdks/runloop-node' && 'depot-ubuntu-24.04' || 'ubuntu-latest' }}
     if: (github.event_name == 'push' || github.event.pull_request.head.repo.fork) && (github.event_name != 'push' || github.event.head_commit.message != 'codegen metadata')
     steps:
-      - uses: actions/checkout@v6
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
 
       - name: Set up Node
         uses: runloopai/setup-node@main
@@ -46,7 +46,7 @@ jobs:
       contents: read
       id-token: write
     steps:
-      - uses: actions/checkout@v6
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
 
       - name: Set up Node
         uses: runloopai/setup-node@main
@@ -64,7 +64,7 @@ jobs:
           github.repository == 'stainless-sdks/runloop-node' &&
           !startsWith(github.ref, 'refs/heads/stl/')
         id: github-oidc
-        uses: actions/github-script@v8
+        uses: actions/github-script@ed597411d8f924073f98dfc5c65a23a2325f34cd # v8.0.0
         with:
           script: core.setOutput('github_token', await core.getIDToken());
 
@@ -94,7 +94,7 @@ jobs:
     runs-on: ${{ github.repository == 'stainless-sdks/runloop-node' && 'depot-ubuntu-24.04' || 'ubuntu-latest' }}
     if: github.event_name == 'push' || github.event.pull_request.head.repo.fork
     steps:
-      - uses: actions/checkout@v6
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
 
       - name: Set up Node
         uses: runloopai/setup-node@main

.github/workflows/publish-npm.yml

@@ -21,7 +21,7 @@ jobs:
       id-token: write # Required for OIDC
 
     steps:
-      - uses: actions/checkout@v6
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
 
       - name: Set up Node
         uses: runloopai/setup-node@main

.github/workflows/release-doctor.yml

@@ -12,7 +12,7 @@ jobs:
     if: github.repository == 'runloopai/api-client-ts' && (github.event_name == 'push' || github.event_name == 'workflow_dispatch' || startsWith(github.head_ref, 'release-please') || github.head_ref == 'next')
 
     steps:
-      - uses: actions/checkout@v6
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
 
       - name: Check release environment
         run: |