v0.5.0 — multiplayer Phases 2 and 3: a server that runs a game and survives being restarted

Phases 0-1 shipped in v0.4.0 (seat/identity split, per-player turn state, the Session boundary).
This lands Phase 2 (server core, one game, no lobby) and Phase 3 (persistence and resumption) per
docs/architecture/multiplayer.md §12. Phases 4-6 (lobby/reconnection, the 22 opponent-directed
cards, StartOS packaging) are still ahead.

Phase 2: src/server/session.ts hosts a game in pure logic (no sockets) on top of game.ts's existing
Game/submit/currentActor/actionMenu; it verifies seat === currentActor(game) itself before calling
submit, since submit() trusts its caller and a server can't. src/server/http.ts and index.ts add
POST /api/game, GET /api/stream (SSE, per-seat), POST /api/intent, and static serving of dist/.
src/sim/frame-delta.ts is a purpose-built per-seat board delta for one live push at a time. Found
and fixed along the way: actionMenu(game, seat) only used seat for the hand field, so a server
computing every connected seat's Menu would have handed the acting player's legal moves to a
waiting seat. Verified with a live end-to-end smoke test (2-player game, two SSE streams, a
rejected intent from the wrong seat, an idempotent resend) plus test/server/session.test.ts and
test/redaction.test.ts. Not verified: an actual browser (none available in this environment).

Phase 3: src/server/persistence.ts writes game.json and turn-timings.json, atomic-rewrite-then-
rename. game.ts gained fromMultiplayerSave, fixing a narration-attribution bug found while testing
it (fromSave's replay loop drops the actor argument, invisible in solitaire, unreadable the moment
there's more than one seat — fromSave itself still has this gap, deliberately untouched). Verified
live: server killed and restarted mid-game, both seats reconnected exactly where they left off.

Two rules bugs found while building this: the New Train phase never implemented its car-placement
round (every car of every train was placed by the Superintendent alone, in every mode, all along —
now reads the round position off tray.consist.length); and victory conditions are now one shared,
configurable GameConfig set across solitaire/competitive/coop instead of a fixed length lookup and
a dead firstToTarget condition.

Also folds in the three fixes already released on the patch line as v0.4.9b/c/d: a switching
train's crew badge failing to draw once it left the Office square, an unload that always took the
westmost car regardless of which was picked, and a legal decision that could render with zero
buttons.

docs/testing/0.5.0-test-plan.md and three reported-bug save files (docs/station-master-seed*.json)
included for reproducibility. tools/jitsi-harness/ deliberately left untracked — unrelated
side-project work, not part of this release. 635 tests, 0 failures.

src/engine/apply.ts

@@ -697,25 +697,24 @@ export function check(s: GameState, player: PlayerIndex, i: Intent): RejectionCo
         ? tray.consist.slice(0, i.count)
         : tray.consist.slice(tray.consist.length - i.count);
       const dropRules = rulesOf(tray);
+      const dropArea = areaOf(s, player);
+      const atOffice = here.row === dropArea.officeCoord.row && here.col === dropArea.officeCoord.col;
       /**
-       * Trains 7/8 Local — "coach must remain on station track if switching", i.e. the coach is
-       * never set out during switching at all.
-       *
-       * The intended reading was "set out only at the Office", but §A.4 makes that unimplementable:
-       * `canDropCarsAt` refuses the Office square outright — "the Office track is Operational Rail,
-       * but Rolling Stock may not be left there" — so "only at the Office" and "nowhere" are the same
-       * rule. What is left is the effect that matters: the Local may shunt its freight car around the
-       * district, and may not abandon its coach at an industry or on a siding while it does.
-       * Flagged in `TODO.md` in case the station track is meant to become a real place to leave one.
+       * Trains 7/8 Local — "coach must remain on station track if switching" — the coach may never
+       * be set out anywhere ELSE while switching. §A.4 now carries an exception for the Office
+       * square (v0.5.0, Jesse's call): any train may cut a coach loose there, which is exactly what
+       * "station track" meant on the card all along. So the coach is refused everywhere except the
+       * Office, rather than everywhere.
        */
-      if (dropRules.coachStaysOnStationTrack && cut.some((c) => c.type === 'coach')) {
+      if (dropRules.coachStaysOnStationTrack && cut.some((c) => c.type === 'coach') && !atOffice) {
         return 'COACH_MUST_STAY';
       }
       const droppedFreight = cut.filter(isFreight).length;
       if (droppedFreight > 0 && !freightBudgetLeft(s, player, tray, here, droppedFreight)) {
         return 'FREIGHT_WORKED_HERE';
       }
-      return canDropCarsAt(areaOf(s, player), here, i.count) ? null : 'CANNOT_DROP_HERE';
+      const coachesOnly = cut.every((c) => c.type === 'coach');
+      return canDropCarsAt(dropArea, here, i.count, coachesOnly) ? null : 'CANNOT_DROP_HERE';
     }
 
     case 'switch.sortConsist': {