v0.7.0 — four game types, a lobby you can read and leave, and a multiplayer game that makes a sound

The multiplayer set-up, the lobby, the start of a game, and four signals a remote client had never
been sent. Reasoning, the preset table and what was verified how: CHANGELOG.md.

- Co-op, Competitive, Cutthroat, Solitaire and Custom, on both screens, from one shared block —
  they had drifted, and each was missing a question the other asked.
- A player reads the whole rule set before taking a seat, may leave a lobby or a running game, and
  keeps a seat across a reload. The host may clear a chair. The browser remembers every game it is
  in, not just the last one.
- The start of a game is drawn: a handoff beat, an announcement, the code and type in the header.
- Sound, the timetable flash, announcements and the just-drawn badge now reach a remote client;
  justDrawn goes to the seat that drew it and nobody else.
- Played on StartOS, which found the rest: an Extra belongs to the player who played it, the board
  never named the Superintendent, bot seats were reported as absent players, and rule section
  numbers are out of every string a player reads.

Also carries the previous session's Heavy Grade documentation work — asked again, answer unchanged.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016JczK5i33ZNSf2PtzZqdhS

src/engine/state.ts

@@ -371,6 +371,15 @@ export type CrewTray = {
    * bug `isBeingMadeUp` was tightened to kill, and an arriving train never carries this.
    */
   beingMadeUp?: boolean;
+  /**
+   * WHOSE TRAIN THIS IS TO BUILD, for an Extra only.
+   *
+   * §7's Extra is loaded by the player who played the card, not by the Superintendent-first round
+   * that fills a Timetabled train — so the tray has to remember them: `pendingExtras` is emptied the
+   * moment the Extra starts, which is before a single car goes on. Undefined on every Timetabled
+   * train, where the round decides instead.
+   */
+  builtBy?: PlayerIndex;
   /**
    * WHERE THE ENGINE SITS IN THE TRAY, as an index into `consist`.
    *
@@ -831,8 +840,15 @@ export type GameState = {
   /**
    * §7 — Extra Trains played from hand, waiting for a free Crew Tray. An Extra is not scheduled:
    * it runs once, immediately, then its card goes to the Salvage Yard (§2.3).
+   *
+   * CARRIES WHO PLAYED IT (2026-08-23, Jesse's call). §7 gives an Extra to the player who played the
+   * card — "may place the Crew Tray at either Division Point ... and may load the consist as he
+   * chooses" — which is a different rule from the Timetabled make-up round, where the table goes
+   * round starting at the Superintendent. This was a bare `number[]`, so the engine could not tell
+   * whose Extra it was and asked whoever the acting order happened to be on: correct in solitaire,
+   * where there is only one player, and wrong at every table.
    */
-  pendingExtras: number[];
+  pendingExtras: { trainNumber: number; player: PlayerIndex }[];
   /**
    * Q9 — train numbers ordered to run a second section. The next New Train Phase makes up an
    * identical train behind the first, if a Crew Tray is free.