fix(release-gate): map index.html to the UI impact domain

Unblock Core+Impact selection for H5 shell title changes.

Co-authored-by: Cursor <cursoragent@cursor.com>

release-gate/impact.mjs

@@ -88,7 +88,7 @@ const IMPACT_RULES = Object.freeze([
   { groups: ['AUTH'], pattern: /(?:auth|access-policy|account|user-permission)/i },
   { groups: ['CFG'], pattern: /(?:config|provider|model-catalog|orchestrator|analytics|disclosure)/i },
   { groups: ['CFG'], pattern: /(?:^|\/)\.env(?:\.example)?$/i },
-  { groups: ['UI'], pattern: /^(?:src\/|public\/)|\.(?:css|scss|tsx|vue)$/i },
+  { groups: ['UI'], pattern: /^(?:src\/|public\/|index\.html$)|\.(?:css|scss|tsx|vue)$/i },
 ]);
 
 const GROUP_DEPENDENCIES = Object.freeze({