feat: add regression patterns to evaluator implement prompt

Three new failure patterns: missing imports after refactoring,
orphaned resource instances, and error detail leakage. These were
observed in a real loop run where the evaluator missed them.

prompts/evaluator/implement.md

@@ -15,3 +15,6 @@ You are evaluating an implementation story. The generator claims to have built a
 - Tests exist but don't assert meaningful behavior
 - Passes typecheck only because types are overly loose
 - Code exists but doesn't actually run
+- Removed an import or variable during refactoring but it's still used elsewhere in the file
+- New instance of a shared resource (e.g., DB connection, rate limiter) instead of using the existing one
+- Error details leaked to HTTP responses (use logging server-side, return generic message to client)