v0.4.9e — five of six playtest bugs: one button per train, and a load that has to go somewhere

Gameplay testing on 0.4.9d returned six reports. Five are fixed; the sixth could not be
reproduced and is written up in TODO.md with the two questions that would pin it down.

TWO TRAINS AT ONE PLATFORM ANSWERED TO ONE BUTTON. `porter.board` and `porter.detrain`
carried no tray, so there was one button per platform however many trains stood at it and
the reducer filled the first empty coach on the A/D tracks. `check` and the reducer were not
even asking the same question: `check` skipped a train whose card refuses passenger work and
the reducer did not. Both intents now carry an optional `trayId`, one function resolves the
train and the coach for check/execute/reduce alike, `legal.ts` offers one candidate per train,
and the label names it.

A LOAD COULD BE MADE AND BROKEN WITHOUT GOING ANYWHERE. A Freight House could unload the
boxcar it had just loaded; a platform could detrain the passengers it had just boarded. Full
Revenue at both ends for a movement that never happened. Jesse's rule: a load made anywhere in
an Office Area may not be broken anywhere in that Office Area, ever — it has to be carried to
another district. The load carries the seat that made it (`RollingStock.origin`), stripped by
`pooled` at every yard push. Measured at -0.60 +/- 0.10 Revenue a game (t = -6.1) over 400
paired deals: 78 worse, 3 better, 319 unchanged — free Revenue coming off the board, not a nerf.

THE GROCER'S WAREHOUSE SHIPPED AND THE REFINERY RECEIVED. Both were `flow: 'both'` on the
reading that "Freight House" was a collective term for exactly those two, and therefore what
§9.3 described. The engine has dealt a Freight House CARD since before v0.4.9, so §9.3 names
it and the argument goes. The card set agrees: all three Refinery modifiers grant +1 outbound.
Refinery outbound-only, Grocer's inbound-only, Freight House the one two-way industry — which
leaves exactly the one same-district pairing the rule above refuses.

NOT REPRODUCED: cars left behind when backing up over them. Five layouts tried, including cars
spotted at an industry; every one couples the lot. Three are pinned in `apply.test.ts`. One way
to create such cars was closed anyway — `flyingSwitch` wrote its cut past `carsOn`.

Both published replays that had gone dead were re-recorded; a rules change retires a save, and
`harness.test.ts` is what catches it.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011nbvwWMef8CuEP6t5cgkTv

TODO.md

@@ -396,6 +396,41 @@ Deferred while planning the server; decisions and reasoning are in `docs/archite
 
 Blocked on a decision, not on work.
 
+- [ ] **NOT REPRODUCED: "when I back up to collect standing cars and, further down the tracks, the
+      caboose, I get the caboose but the cars remain. I can later drive right through them."**
+      Reported against v0.4.9d by a playtester (not Jesse, who forwarded it and could not add detail;
+      his guess was that the cars were spotted at an industry).
+
+      **What was tried, all of which works.** Cars on plain track on the way to the caboose; cars
+      SPOTTED AT AN INDUSTRY on the way; the train's own cut standing on the square it is pulling out
+      of; a stale `standingWest` on the intermediate card; the industry locked by MEN AT WORK (which
+      correctly blocks the whole route rather than letting the crew past). Every one couples the lot.
+      The first three are pinned in `apply.test.ts` — "backing up over a cut to something beyond it
+      takes both" — so if the case is found later it is somewhere none of them cover.
+
+      **Why it is hard to make happen.** Coupling is mandatory (§A.4) and `exploreMoves` accumulates
+      what it meets card by card, so a route that reaches the caboose has already met everything
+      between. `carsOn` (`state.ts`) is the SINGLE answer to "what is standing here", and the movement
+      walk, the sweep in `carsCoupled` and every renderer all ask it — so cars a train can drive
+      through would have to be cars that are on screen and not in `carsOn`, and there is no such
+      place. (One route to one was closed anyway: `flyingSwitch`'s reducer wrote the cut straight into
+      `industryTrack`, which for a Passenger Facility is not where `carsOn` looks. `check` refuses a
+      non-freight target, so it never fired.)
+
+      **The two questions that would settle it**, for whoever has the board: was there a SECOND route
+      to the caboose — a parallel row, or a turnout — so the move could have gone round the cars? And
+      what did the move button say it would couple? The label names every car (`describeIntent`), so a
+      button that read "couples caboose" and one that read "couples 2 boxcars, caboose" are different
+      bugs: the first is route selection, the second is the sweep.
+
+- [ ] **An unload does not check the facility's commodity.** `laborer.beginUnload` gates on
+      `allows.inbound`, a loaded car, an empty of that type in the Division Yard and room in the red
+      box — but never on `facilityCarTypes(f)`, which `freightAgent.stockOutbound` does check. So a
+      Freight House (boxcars) will unload a hopper. Found reading the code for the v0.4.9e district
+      rule, not from play. Low impact today because the district rule now refuses the only same-Office
+      pairing that made it easy to hit, and because the bot spots matching cars — but it is a rule the
+      engine states in one direction and not the other.
+
 - [ ] **WHERE THE LOCAL'S COACH STANDS WHILE ITS ENGINE WORKS (§A.4) — now hit in play, still open.**
       Trains 7/8 print "coach must remain on station track if switching", read as "the coach is never
       set out". A cut comes off an OUTER end, so a coach on one outer end with the engine on the