Share a turn with the world: /watch links, cards and chrome included

The share button lands on the instant replay. One click mints a slug —
persistent, unguessable, one per (room, turn) — and copies a /watch
link anyone can open: the server rebuilds exactly that turn for the
nameless SPECTATOR, public knowledge only, none of the rest of the
game visible. The page arrives with its OpenGraph card pre-baked into
the head (crawlers never run the app): the turn's title and round in
the text, and an og.png of the maze itself — cells, walls, doors, warp
mouths, homes, standees — painted server-side and PNG-encoded with
nothing but node's own zlib. The viewer page wears its chrome: the
WIZ-WAR masthead linking home, the turn's title, the reel opening
straight into the turn-owner's eyes with a "watch it again" loop, and
a footer that says what this table is and deals the visitor in.

The share page loads as its own entry so a shared link never drags the
full app's socket appetite along; the reel's modal scrim learns to
stand in a page instead of over one.

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

packages/server/src/rooms.ts

@@ -428,7 +428,10 @@ const TURN_BOUNDARY = new Set(["turnStarted", "extraTurnStarted", "turnSkipped"]
  */
 export function momentSteps(room: Room, playerId: PlayerId, turnIndex: number): CatchUpStep[] | { error: string } {
   if (!room.state) return { error: "game not started" };
-  if (!room.players.includes(playerId)) return { error: "you hold no seat in this room" };
+  // The SPECTATOR builds share pages: public knowledge only, no seat.
+  if (playerId !== SPECTATOR && !room.players.includes(playerId)) {
+    return { error: "you hold no seat in this room" };
+  }
   const MAX_STEPS = 80;
   const { state: fresh, events: dealt } = createGame(room.state.config);
   let current = fresh;