[Good first issue]: Add unit tests for parseBuilderCirclePoolMode

[FrankezeCode]

Summary

Builder Circles supports rsvp, city, and hybrid pool modes. Add tests for the parser helper to lock in default/fallback behavior.

What should change?

• Add tests in test/BuilderCircleMatching.ts for parseBuilderCirclePoolMode
• Cover: rsvp, city, hybrid, invalid value, undefined, mixed case

Acceptance criteria

Parser returns correct mode for valid inputs,
Invalid/empty input defaults to hybrid,
Tests pass.

Checklist of done conditions:

• 5+ test cases added
• Uses node:test / existing test patterns
• Tests pass
• No unrelated test changes

How to test

Run test file :
node --test test/BuilderCircleMatching.ts