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/legal.ts

@@ -79,7 +79,7 @@ function candidates(s: GameState, player: PlayerIndex): Intent[] {
       out.push(...localOpsCandidates(s, player));
       break;
     case 'newTrain':
-      out.push(...newTrainCandidates(s));
+      out.push(...newTrainCandidates(s, player));
       break;
     case 'loadUnload':
       out.push(...loadUnloadCandidates(s, player));
@@ -257,7 +257,7 @@ function localOpsCandidates(s: GameState, player: PlayerIndex): Intent[] {
   return out;
 }
 
-function newTrainCandidates(s: GameState): Intent[] {
+function newTrainCandidates(s: GameState, player: PlayerIndex): Intent[] {
   const out: Intent[] = [];
   for (const [trayId] of s.trays) {
     for (const carType of CAR_TYPES) {
@@ -279,7 +279,9 @@ function newTrainCandidates(s: GameState): Intent[] {
    * is placed. In the middle of the railroad — an Interchange, a Control Point — both ways are real
    * runs, so those are offered twice, once per direction.
    */
-  for (const trainNumber of s.pendingExtras) {
+  // Only the player who played it is offered anywhere to put it (§7) — `check` refuses anyone else
+  // with NOT_YOUR_EXTRA, and offering options that are certain to be refused is how a menu lies.
+  for (const { trainNumber } of s.pendingExtras.filter((x) => x.player === player)) {
     for (const side of ['west', 'east'] as const) {
       out.push({ type: 'newTrain.startExtra', trainNumber, start: { kind: 'divisionPoint', side } });
     }