Card wave 2: durations, doors, teleports, modifiers; harden room auth

Duration system: sustained effects expire at the start of the caster's
turns; SLOW (movement 1, no number cards, attack every other turn),
NO SPELL, MEDUSA (paralysis + damage immunity), INVISIBLE (1-in-4 hit
roll), SHRINK (50% miss, movement 2). Doors: PICK LOCK and MASTER KEY
(displayed, reusable) unlock adjacent doors until end of turn, REMOVE
LOCK is permanent, JAM LOCK seals a door for everyone. Movement:
TELEPORT (4 spaces through walls, ends movement), PASS THROUGH WALL
charges, POWER RUN (life for spaces), SWAP (consumes movement),
GO AWAY (knockback + lost turn), TELEPORT OPPONENT. Card warfare:
CARD ERASURE (named), THOUGHT-STEAL (2 random via seeded RNG),
TELEPATH (private hand reveal), POWER DRAIN (damage feeds the caster),
SUDDEN DEATH, STONE DEAD, WIZARDBLADE (same-square, number-powered,
stays displayed). Cast modifiers: AMPLIFY doubles power/duration
(stackable x2), ADD permits two number cards, EXTEND doubles duration;
REVERSE heals instead of harms but keeps secondary effects. Counters
now also halve durations (BLUNT) and split them (REFLECTION).

Security (from review findings): room codes and game seeds now come
from node:crypto, and every seat gets a secret token — reclaiming a
name in a room requires its token, closing the impersonation hole.

29 cards implemented; 51 tests passing.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

packages/server/src/rooms.ts

@@ -2,6 +2,7 @@
 // the append-only command log (the seed + log IS the game — the basis for
 // replays and async play). Clients get per-player redacted views and events.
 
+import { randomBytes, randomInt } from "node:crypto";
 import {
   applyCommand,
   createGame,
@@ -25,6 +26,8 @@ export interface Room {
   id: string;
   hostId: PlayerId;
   players: PlayerId[]; // join order
+  /** Per-player secrets: reclaiming a seat requires the matching token. */
+  tokens: Map<PlayerId, string>;
   seed: number;
   state: GameState | null; // null until started
   log: LoggedCommand[];
@@ -38,35 +41,47 @@ const ROOM_CODE_ALPHABET = "ABCDEFGHJKLMNPQRSTUVWXYZ23456789";
 function makeRoomCode(): string {
   let code = "";
   for (let i = 0; i < 4; i++) {
-    code += ROOM_CODE_ALPHABET[Math.floor(Math.random() * ROOM_CODE_ALPHABET.length)];
+    code += ROOM_CODE_ALPHABET[randomInt(ROOM_CODE_ALPHABET.length)];
   }
   return rooms.has(code) ? makeRoomCode() : code;
 }
 
-export function createRoom(hostId: PlayerId): Room {
+export function createRoom(hostId: PlayerId): { room: Room; token: string } {
+  const token = randomBytes(16).toString("hex");
   const room: Room = {
     id: makeRoomCode(),
     hostId,
     players: [hostId],
-    seed: Math.floor(Math.random() * 0xffffffff),
+    tokens: new Map([[hostId, token]]),
+    seed: randomInt(0, 0xffffffff),
     state: null,
     log: [],
     events: [],
   };
   rooms.set(room.id, room);
-  return room;
+  return { room, token };
 }
 
 export function getRoom(id: string): Room | undefined {
   return rooms.get(id.toUpperCase());
 }
 
-export function joinRoom(room: Room, playerId: PlayerId): string | null {
-  if (room.state) return "game already started";
-  if (room.players.includes(playerId)) return null; // rejoin is fine
-  if (room.players.length >= 4) return "room is full";
+export function joinRoom(
+  room: Room,
+  playerId: PlayerId,
+  token: string | null,
+): { token: string } | { error: string } {
+  if (room.players.includes(playerId)) {
+    // Reclaiming an existing seat requires that seat's secret.
+    if (token && room.tokens.get(playerId) === token) return { token };
+    return { error: "that wizard name is taken in this room" };
+  }
+  if (room.state) return { error: "game already started" };
+  if (room.players.length >= 4) return { error: "room is full" };
+  const fresh = randomBytes(16).toString("hex");
   room.players.push(playerId);
-  return null;
+  room.tokens.set(playerId, fresh);
+  return { token: fresh };
 }
 
 export function startGame(room: Room): { events: GameEvent[] } | { error: string } {