ci: opt Firebase action into Node.js 24 runtime

The FirebaseExtended/action-hosting-deploy action still runs on
Node.js 20 which GitHub will deprecate on June 2, 2026. Scope the
FORCE_JAVASCRIPT_ACTIONS_TO_NODE24 flag to just the Firebase deploy
step in both deploy workflows to validate compatibility early.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: sserrata

.github/workflows/deploy-live.yml

@@ -104,6 +104,7 @@ jobs:
           target: ${{ secrets.FIREBASE_SITE }}
         env:
           FIREBASE_CLI_PREVIEWS: hostingchannels
+          FORCE_JAVASCRIPT_ACTIONS_TO_NODE24: true
 
   cache_prod_screenshots:
     name: Cache Prod Screenshots

.github/workflows/deploy-preview.yml

@@ -200,6 +200,7 @@ jobs:
           totalPreviewChannelLimit: 25
         env:
           FIREBASE_CLI_PREVIEWS: hostingchannels
+          FORCE_JAVASCRIPT_ACTIONS_TO_NODE24: true
 
   visual_diff:
     name: Visual Diff