Fixed critical bug where ApiRequestPanel allowed submitting malformed JSON without validation, causing API call failures.
- ApiRequestPanel.tsx: Added real-time JSON validation with editable mode
- ApiRequestPanel.css: Styled validation UI with error states
- ApiRequestPanel.test.tsx: Added 17 comprehensive tests
- Test files: Created standalone validation tests and interactive demo
✅ Real-time JSON validation on every keystroke
✅ Inline error messages with specific syntax details
✅ Submit button auto-disabled for invalid JSON
✅ Accessibility compliant (ARIA attributes)
✅ Backward compatible (opt-in editable mode)
- JSON validation: 13/13 passed ✅
- Integration tests: 8/8 passed ✅
- TypeScript: No errors ✅
0284b16f - Pushed to main branch