refactor(games): overhaul WS game system with improved UX and solo test support

Backend:
- Fix session never being attached to ws.data at upgrade time
- Add GameServer class: connection registry, per-connection room tracking,
  automatic room cleanup on disconnect via ws.data.rooms
- Replace ws-handler.ts with typed event-driven architecture using mitt
- Remove redundant subscription tracking from RoomManager
- Add JOIN_RESULT with player/spectator lists replacing error-as-control-flow
- Add SESSION_REPLACED for multi-tab same-account detection
- Add FILL_ROOM command for admin solo testing (fills empty slots with host)
- Fix dual-schema routing; remove game types from WsMessageSchema
- Per-player personalized views sent directly after each action

Chess plugin:
- Allow same-player (solo) mode: skip color/turn ownership checks
- Fix forfeit and disconnect handling in solo mode (winner: null)

Frontend:
- Click-to-move with legal move dots and last-move highlight
- Auto-scroll move history, forfeit confirmation, turn-reactive board border
- JOIN_RESULT initialises player/spectator lists immediately on join
- Contextual connecting state, player slot cards in waiting room
- Copy-invite button with Copied! flash, Back to Lobby CTA on finish
- Session-replaced warning banner with Rejoin here action
- Lobby passes preferAs intent through route state
- Admin waiting room shows Start Solo Test button

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

panel/src/lib/useGameRoom.ts

@@ -1,5 +1,6 @@
-import { useEffect, useState, useCallback } from "react";
+import { useEffect, useState, useCallback, useRef } from "react";
 import { useWebSocket } from "./useWebSocket";
+import { useNavigate } from "react-router-dom";
 
 interface PlayerInfo {
     discordId: string;
@@ -14,10 +15,17 @@ interface GameRoomState {
     isSpectator: boolean;
     gameOver: { winner: string | null; reason: string } | null;
     error: string | null;
+    sessionReplaced: boolean;
 }
 
-export function useGameRoom(roomId: string, userId: string, role?: string) {
+export function useGameRoom(roomId: string, userId: string, role?: string, preferAs: "player" | "spectator" = "player") {
     const { send, subscribe, connected } = useWebSocket();
+    const navigate = useNavigate();
+    const navigateRef = useRef(navigate);
+    useEffect(() => {
+        navigateRef.current = navigate;
+    }, [navigate]);
+
     const [state, setState] = useState<GameRoomState>({
         gameState: null,
         players: [],
@@ -26,17 +34,29 @@ export function useGameRoom(roomId: string, userId: string, role?: string) {
         isSpectator: false,
         gameOver: null,
         error: null,
+        sessionReplaced: false,
     });
 
     useEffect(() => {
         if (!connected) return;
 
-        send({ type: "JOIN_ROOM", roomId, as: "player", role: role ?? "player" });
+        send({ type: "JOIN_ROOM", roomId, preferAs, role: role ?? "player" });
 
         const unsubscribe = subscribe((msg: any) => {
             if (msg.roomId && msg.roomId !== roomId) return;
 
             switch (msg.type) {
+                case "JOIN_RESULT":
+                    setState(prev => ({
+                        ...prev,
+                        isSpectator: msg.joinedAs === "spectator",
+                        roomStatus: msg.roomStatus,
+                        players: msg.players ?? prev.players,
+                        spectators: msg.spectators ?? prev.spectators,
+                        gameState: msg.state !== undefined ? msg.state : prev.gameState,
+                    }));
+                    break;
+
                 case "GAME_STATE":
                     setState(prev => ({ ...prev, gameState: msg.state, roomStatus: "playing" }));
                     break;
@@ -51,7 +71,7 @@ export function useGameRoom(roomId: string, userId: string, role?: string) {
 
                 case "PLAYER_JOINED":
                     setState(prev => {
-                        if (msg.as === "spectator") {
+                        if (msg.joinedAs === "spectator") {
                             const isMe = msg.player.discordId === userId;
                             return {
                                 ...prev,
@@ -60,7 +80,7 @@ export function useGameRoom(roomId: string, userId: string, role?: string) {
                                 roomStatus: prev.roomStatus === "connecting" ? "waiting" : prev.roomStatus,
                             };
                         }
-                        
+
                         const isMe = msg.player.discordId === userId;
                         return {
                             ...prev,
@@ -87,11 +107,14 @@ export function useGameRoom(roomId: string, userId: string, role?: string) {
                     }));
                     break;
 
+                case "SESSION_REPLACED":
+                    setState(prev => ({ ...prev, sessionReplaced: true }));
+                    break;
+
                 case "ERROR":
-                    if (msg.message === "Game already started" || msg.message === "Room is full") {
-                        send({ type: "JOIN_ROOM", roomId, as: "spectator" });
-                    } else if (msg.message === "Room not found") {
+                    if (msg.message === "Room not found") {
                         setState(prev => ({ ...prev, roomStatus: "not_found" }));
+                        setTimeout(() => navigateRef.current("/games"), 2000);
                     } else {
                         setState(prev => ({ ...prev, error: msg.message }));
                     }
@@ -114,5 +137,14 @@ export function useGameRoom(roomId: string, userId: string, role?: string) {
         send({ type: "LEAVE_ROOM", roomId });
     }, [roomId, send]);
 
-    return { ...state, sendAction, leaveRoom };
+    const rejoin = useCallback(() => {
+        send({ type: "JOIN_ROOM", roomId, preferAs, role: role ?? "player" });
+        setState(prev => ({ ...prev, sessionReplaced: false }));
+    }, [roomId, preferAs, role, send]);
+
+    const fillRoom = useCallback(() => {
+        send({ type: "FILL_ROOM", roomId });
+    }, [roomId, send]);
+
+    return { ...state, sendAction, leaveRoom, rejoin, fillRoom };
 }