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

test/mainline-cards.test.ts

@@ -313,6 +313,7 @@ describe('Flying Switch rolls a cut into an industry', () => {
       geometry: { kind: 'track', geometry: 'straight' },
       baseOperationalRail: true,
       standing: [],
+      standingWest: 0,
       facility: null,
       modifiers: [],
       enhancements: [],