Scaffold project and author 14-phase roadmap

Browser co-op kitchen game: FastAPI + native WebSockets, server-authoritative
20 Hz simulation, in-memory anonymous lobbies, data-driven YAML levels, Canvas 2D
vanilla ES-module client with locally authored SVG art and no external CDNs.

.agents/PLAN.md records the LOCKED decisions; .agents/user_stories/ holds the 12
flow contracts; .agents/phases/todo/ breaks them into 14 sequential, test-gated
phases (71 task files), each leaving the app launchable and the suite green.

LLM-Generated: true

.agents/user_stories/US-03_ready_up_and_start.md

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+# US-03 — Ready up and start from the lobby
+
+**As a** host,
+**I want to** pick the level and start once everyone is ready,
+**so that** the group begins together on the same kitchen.
+
+## Acceptance criteria
+1. The lobby lists every seat: name, ready state, host crown, connection state.
+2. Any player can toggle *Ready*; the host can pick any **unlocked** level from a
+   list showing name, target score, time limit, and difficulty pips.
+3. *Start* is enabled for the host when ≥ 1 non-host player is ready (or the host is
+   alone — solo play is allowed).
+4. Starting begins a 3-2-1 `countdown` shown identically on all clients, then the
+   first `snap` arrives.
+5. Non-host players cannot start or change level; the attempt shows a disabled control
+   (no console errors, no silent failure).
+6. If the host leaves in `LOBBY`, host status transfers to the lowest occupied seat;
+   in `PLAYING` the round continues.
+7. Someone leaving during `COUNTDOWN` cancels the countdown back to `LOBBY`.
+8. Starting creates a round record in the in-memory session store.
+
+## E2E suite
+`tests/e2e/test_us03_ready_and_start.py` — two contexts: ready toggles visible to
+both, non-host start rejected, countdown then both screens show the kitchen.
+
+## Phases
+`05_anonymous_lobbies_and_room_lifecycle`, `06_realtime_websocket_protocol`,
+`07_canvas_client_and_hud`