Enable early hints debug mode

Add debug: true to early hints configuration to output debug info
as HTML comments in production, making it easier to verify that
early hints are working correctly.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

Author: justin808

config/shakapacker.yml

@@ -67,3 +67,4 @@ production:
   # Early hints configuration
   early_hints:
     enabled: true
+    debug: true # Outputs debug info as HTML comments