Add PR example guideline to CLAUDE.md

Author: ryukzak

CLAUDE.md

@@ -99,6 +99,7 @@ FHIR Package → TypeSchema Generator → TypeSchema Format → Code Generators
 
 - PR body should be a flat bullet list summarizing changes — no section headers, no test plan.
 - Keep bullets concise and focused on what changed, not why.
+- When a PR changes generated code or user-facing API, include before/after examples in the PR body.
 
 ## Development Guidelines