Phase 12 — idle/prompting/creating/done/error state machine that drives
the 700ms compress-and-rise animation and calls projectsApi.create with
a brainstormer payload (goal, acceptance criteria, gates, engineer
template). Also exports buildCreatePayload helper for testing.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
