Two-tree integration: proof generation UI + dual-system deployment

[ejmockler]

Summary

The proof generation UI must handle both single-tree and two-tree proof paths, including progress indicators for mobile proving times that may reach 20-30 seconds on mid-range devices.

Severity: Required for two-tree deployment
Source: Two-Tree Architecture Spec, Performance Agent Review
Related voter-protocol tracking: Phase 5 remaining items

Requirements

Dual-System Proof Generation

• Detect credential type (single-tree vs two-tree)
• Route to NoirProver or TwoTreeNoirProverAdapter accordingly
• Both paths produce a proof + public inputs for on-chain verification
• Submission API must accept both formats during the transition period

Progress UI

• Two-tree proofs generate ~25.5K constraints (2.3× single-tree)
• Estimated proving times:
  • iPhone 14+: ~14s ✅
  • Android flagship: ~14-17s ✅
  • Mid-range (2yr old): ~20-28s ⚠️
  • Low-end: ~30-40s ⚠️
• Progress bar or spinner with elapsed time for proofs exceeding 15s
• Timeout handling with user-friendly retry option (suggest closing other tabs)

Deployment Coordination

• Both verifier contracts (single-tree DistrictGate and two-tree DistrictGate) must be active
• API endpoints accept both proof formats
• Feature flag or credential-type-based routing
• Monitoring: track proof type distribution during rollover

Pitfalls

• WASM thread contention on mobile — proof generation should block UI minimally (use Web Worker)
• Two-tree proofs have 29 public inputs vs 5 — the submission payload is significantly larger
• Network timeout on slow connections with large payloads — consider chunked upload or compression
• The 6-month rollover means both systems run in parallel for the entire period — test resource usage

Acceptance Criteria

• Proof generation routes correctly based on credential type
• Progress UI for proofs > 15s
• Timeout + retry UX for proofs > 30s
• Web Worker for non-blocking proof generation
• Both proof types accepted by submission API
• Feature flag for two-tree activation
• Mobile device testing on target matrix (iPhone 12+, Pixel 6+, mid-range)