the Roster Pass: every train at the Office visible

Builds "The Roster Pass" / "Two Trains, One Card" (station display for
multiple trains at one Office). The Office is the one square where
more than one train may legally stand at once (one per A/D track), and
CellView.train had room for exactly one — a second train at a busy
Station was counted in the old A/D pips and never drawn.

CellView.train -> CellView.trains: TrainView[], seat-filtered and
collecting every match rather than the first (fixes a latent
cross-district leak in the process: trainOnCard never checked seat).
The A/D pips are replaced with one roster chip per A/D track, always,
free or occupied; clicking a chip sets selectedCrew, wiring the board
and the action panel to the same value.

standingWest moves from CrewTray to TrackCard: two trays sharing one
Office card need one shared split, not one each, and there is no such
thing as "west of one particular A/D track". No save migration — Save
replays through the engine — and a stale value on an emptied card is
inert because nothing reads a split with no train standing there.

The Division map's Office cell is now sized by A/D capacity rather
than occupancy, so it holds still as trains arrive and leave; chips
lay into fixed slots instead of centre-spreading onto the Limits cards
either side.

584 tests, 0 failures. Verified end-to-end against the built app and a
direct render of a 4-train Terminal (screenshotted).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SAt2YCXgd5qCjBcF2x34aK

src/engine/track.ts

@@ -316,15 +316,6 @@ export type MoveContext = {
   consistSize: number;
   /** The tray making the move, so it does not block itself. */
   self: TrayId;
-  /**
-   * How many cars on the START card stand west of this train (`CrewTray.standingWest`).
-   *
-   * The walk begins at `neighbour(start, initialExit)` and never looked at the start card at all, so
-   * a train drove straight through the cut it had just set out — in both directions, and without
-   * counting it against the four-car limit. Coupling is mandatory (§A.4) and a cut on your own
-   * square is no exception: pulling out through the end it sits at picks it up again.
-   */
-  standingWest?: number;
 };
 
 function cardAt(area: OfficeArea, c: GridCoord): TrackCard | undefined {
@@ -459,7 +450,7 @@ export function exploreMoves(
    *
    * Ordered nearest-first like every other card's, so it simply seeds the accumulator.
    */
-  const ownCut = cutTowards({ standingWest: ctx.standingWest }, carsOn(startCard), initialExit);
+  const ownCut = cutTowards(startCard, carsOn(startCard), initialExit);
   const startKey = coordKey(start);
   const queue: Frontier[] = [
     {