ci: allow temporary Linux runner override

Author: BitCook

.github/workflows/release.yml

@@ -12,7 +12,7 @@ permissions:
 
 jobs:
   validate:
-    runs-on: ubuntu-latest
+    runs-on: ${{ vars.AGENTBOOT_LINUX_RUNNER || 'ubuntu-latest' }}
     steps:
       - uses: actions/checkout@11d5960a326750d5838078e36cf38b85af677262 # v4
         with:
@@ -28,7 +28,7 @@ jobs:
           node --check cloudflare/worker.js
 
   online:
-    runs-on: ubuntu-latest
+    runs-on: ${{ vars.AGENTBOOT_LINUX_RUNNER || 'ubuntu-latest' }}
     steps:
       - uses: actions/checkout@11d5960a326750d5838078e36cf38b85af677262 # v4
         with:
@@ -49,7 +49,7 @@ jobs:
             pages/VERSION
 
   offline-linux:
-    runs-on: ubuntu-latest
+    runs-on: ${{ vars.AGENTBOOT_LINUX_RUNNER || 'ubuntu-latest' }}
     steps:
       - uses: actions/checkout@11d5960a326750d5838078e36cf38b85af677262 # v4
         with:
@@ -129,7 +129,7 @@ jobs:
   publish:
     needs: [validate, online, offline-linux, offline-windows, macos-smoke]
     if: github.ref_type == 'tag'
-    runs-on: ubuntu-latest
+    runs-on: ${{ vars.AGENTBOOT_LINUX_RUNNER || 'ubuntu-latest' }}
     environment: release-production
     permissions:
       contents: write

tests/test_release_workflow.py

@@ -33,6 +33,7 @@ def test_release_supports_prerelease_dry_run_and_tag_only_publish(self):
         self.assertIn("install-offline.ps1\" -Agents codex", text)
         self.assertIn("runs-on: macos-15-intel", text)
         self.assertIn("PLATFORMS=darwin-x64", text)
+        self.assertIn("vars.AGENTBOOT_LINUX_RUNNER || 'ubuntu-latest'", text)
 
     def test_live_verifier_covers_primary_and_mirror(self):
         text = (ROOT / "scripts/verify-live-release.py").read_text(encoding="utf-8")