ci: drop pre-merge rewire branch from build triggers

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XpCz2RvuxV5uV8bFwCEpkL

Author: claude

.github/workflows/build-release.yml

@@ -6,7 +6,7 @@ name: Build firmware
 
 on:
   push:
-    branches: [main, 'rewire/valar-core']   # rewire/* verifies the branch pre-merge; remove after merge
+    branches: [main]
     tags: ['v*']
   pull_request:
   workflow_dispatch: