Hack Day: Side-by-Side Alternative GUI Framework

## Summary
Build a side-by-side alternative frontend implementation (mobile-friendly and modern UX) while keeping existing UI path intact.

## Jump-Off State(s)
- `009-order-management-matcher` or `012-platform-convergence-c3`

## Graph Intent
`optional branch`

## Scope
- Implement equivalent key workflows in an alternate web framework.
- Run both UIs against same backend contracts.
- Compare code structure, maintainability, and responsiveness.

## Acceptance Criteria
- Core workflows work in both UIs with shared APIs/events.
- Comparative doc exists (dev ergonomics + UX outcomes).
- No regressions to existing canonical UI path.

## Decision Gate (Promote/Park)
Promote only if there is clear long-term maintainability or UX advantage.

Start at the `009-order-management-matcher` or `012-platform-convergence-c3` state and first map the canonical UI's key workflows, shared backend contracts, and events. Done means equivalent workflows run in both UIs, a comparative developer-ergonomics and UX document exists, and the canonical UI has no regressions before the Promote/Park decision.

Written by the indexing model from the issue text.