## Summary
- Restructure the refinement system prompt into clear numbered sections
(Preserve Behavior, Minimize Diff, Revert Anti-Patterns, Maintain
Readability) with an explicit 6-step refinement process
- Extract inline prompt strings into separate markdown files
(`refinement_system_prompt.md`, `refinement_user_prompt.md`), matching
the convention used by other optimizer prompts
- Add `AuthenticatedRequest` type hint to `refine()` endpoint and fix
grammar in tool use section
## Test plan
- [ ] Verify refinement endpoint still works end-to-end with a test
optimization candidate
- [ ] Confirm prompt content is loaded correctly from markdown files at
startup
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Co-authored-by: claude[bot] <41898282+claude[bot]@users.noreply.github.com>
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