Document limits, load control and performance

- New docs/09-limits-and-performance.md: principles, all protection
  layers, what players see, configuration reference, measurements,
  tuning guide, monitoring and how to test
- Server chapter summarises the limits and links to chapter 9; circuit
  breaker description and AI_MAX_INFLIGHT default corrected
- Architecture: new files in the layout, design decisions for load
  handling; docs index lists chapter 9
- Protocol, AI and operations chapters link to chapter 9; test counts
- Root and component READMEs describe the limits and settings

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

wizard_website/README.md

@@ -18,9 +18,12 @@ development, or `VITE_WS_URL` at build time to use an absolute websocket URL ins
 ## Structure
 
 - `src/api/` — protocol types and the `useWizard` hook (websocket connection,
-  reconnect with a per-tab session token, game state)
+  reconnect with a per-tab session token, game state, server load status; slow
+  retries when the server is full)
 - `src/components/` — reusable UI (button, playing card, modal, toasts)
-- `src/screens/HomeScreen` — enter a name, create or join a lobby
-- `src/screens/LobbyScreen` — lobby code, players, AI players, rule options, start
+- `src/screens/HomeScreen` — enter a name, create or join a lobby (Create is disabled with a
+  notice while the server is busy)
+- `src/screens/LobbyScreen` — lobby code, players, AI players, rule options, start (disabled
+  with a notice while the server is busy)
 - `src/screens/GameScreen` — the table: seats, trick, hand, bidding, trump choice,
   scoreboard, round summary, game over