Refactor web-react: SSE app state + sendCommand (#43)

[enricopiovesan]

Summary

• Replace useExecution polling with useAppState SSE subscription to /apps/traverse-starter/events
• Add sendCommand() for POST /apps/{app_id}/commands (059); remove pollExecution
• Update App to submit via command dispatch and render runtime-owned states (idle / processing / results / error)

Governing Spec

• 033-http-json-api — app SSE events
• 059-http-command-dispatch — command dispatch
• 052-app-state-machine — runtime-owned states

Project Item

• Closes Refactor web-react: replace useExecution polling with runtime SSE state subscription #43
• Project 2 item for Refactor web-react: replace useExecution polling with runtime SSE state subscription #43 (In Progress → Done on merge)

Definition of Done

• useExecution.ts deleted
• useAppState.ts connects via EventSource and maps event payloads only
• sendCommand() on traverseClient.ts
• App.tsx submits via sendCommand, renders from useAppState
• Unit tests mock SSE events instead of HTTP polling
• Coverage target updated to hooks/useAppState.ts
• phase1_smoke.sh unchanged (Phase 1 execute/poll path still valid)

Validation

• npm test / npm run typecheck / npm run lint in apps/traverse-starter/web-react
• bash scripts/ci/coverage_gate.sh
• bash scripts/ci/repository_checks.sh

Architecture boundary

• UI maps runtime state/output only; no local transition or business-field logic
• Public HTTP/SSE surface only (no private Traverse internals)

Checklist

• Issue linked and Project 2 item updated
• Updated AGENTS.md platform table if this changes platform status (N/A — web already shipped; pattern upgrade only)
• No business logic added to UI layer
• CI gates pass locally where applicable

Made with Cursor