W4-01: E2E smoke: submit to index to UI

[sp0oby]

Documented path: anvil + API + UI.

[sp0oby]

Status update: backend portion done (commit 29cd1fc — backend/tests/e2e/full-roundtrip.test.ts spawns two real Anvil instances, deploys the full stack, drives a full Alice/Bob P2P swap through the indexer + matching loop + chain submitters with the LZ relayer, and asserts both balances move on-chain). UI-side E2E is Stage 5 — needs the real contract wiring (Epic #3) before a Playwright/Cypress flow can exercise the submit -> match -> settle path through the browser. Leaving open as the umbrella for the UI E2E once Stage 5 lands.

[sp0oby]

Status update post-Stage 5.Z (b886413):

Coverage today:

• Backend E2E (4/4 vitest): two real Anvils, full P2P round-trip with cross-chain LayerZero relay, settles end-to-end
• Local-stack manual flow: npm run local-stack boots 2 Anvils + indexers + matching loop + auction orchestrator + LZ relayer + reference solver bot + REST/WS API in a single process; user can connect MetaMask, submit intents on /swap, see them indexed on /history, watch state transitions on /intent/[hash] over WebSocket
• Frontend lint + build + 40/40 vitest unit pass
• Backend lint + 105/105 vitest unit pass

Verified via local-stack manual flow:

• Submit → PENDING (intent indexed, surfaces on /history immediately)
• PENDING → AUCTIONING (auction orchestrator opens auction after delay)
• Solver bid lands in /api/intents/:hash/proposals and renders on the status page with winner badge
• Tx hash chips appear on the status page (Submit / Match / Settle / Cancel / Refund) with proper block-explorer URLs

Remaining for full E2E smoke parity with this issue:

• Auction-fallback path: executeWinningProposal emits WinnerSelected but doesn't chain executeMatching — Stage 6 carry-over
• Sepolia / Base Sepolia deploy (W2-03: Contract deployment scripts #16) to verify against real LayerZero V2 endpoints

P2P match path is fully operational; auction-fill path needs the protocol-level fix tracked as a Stage 6 item.