v0.6.2 — an Extra starts where you put it, a train card is never discarded

Three more from the v0.4.9e gameplay-testing round, filed as Gitea issues, plus two bugs found
underneath them. Gitea#2 is diagnosed but NOT fixed: it needs a ruling, and the reasoning is in
TODO.md under Play Balance.

GITEA#4 — AN EXTRA STARTS WHERE THE PLAYER PUTS IT. Only one Division Point was ever offered,
chosen by number parity. The number no longer decides an Extra's direction — the start does, which
supersedes the recorded ruling that "the number decides, like everything else on the timetable".
The two cannot both hold: an odd, westbound Extra placed at the WEST end would leave the Division
on its first move having crossed nothing, and be paid for the run. Either end now runs the train
away from itself; at an Interchange or a Control Point the player picks the direction. The
Interchange start is a YARD, off the running line, which is what makes the Superintendent clause
work: placing it can never force a collision, a guaranteed one holds it there for another Stage,
and a potential one is the Superintendent's to rule on — exactly evaluateClearance's `blocked` and
`ask`, so nothing new decides collisions. Where an Extra may start is now a house rule
(divisionPointsOnly / ownOffice / anyOffice, defaulting to what the engine already did). The
legacy `atSeat` intent field still replays as it always meant.

FOUND UNDERNEATH IT: an Extra started away from a Division Point ran empty. isBeingMadeUp tested
position alone, so the Control Point start has been shipping since it was added with a train that
could never be given a consist. Found by playing it, not by the tests, which had only asserted
where the tray landed.

FOUND UNDERNEATH IT: collide left the wrecks on the card. Destroyed trains kept their Transit
entries, and evaluateClearance counts every transit as an occupant, so one rear-end collision
permanently poisoned that Mainline card for every later train.

THE MAINLINE CARDS WERE ROLLED, NOT DEALT — drawn from the nine types with replacement, so a
Division could hold two Interchanges and Plains carried the weight of a card printed once. "An
Extra may start at the Interchange if one is on the board" only reads as a rule if the board holds
at most one. Now dealt from the printed deck without replacement, verified over 1600 deals. This
re-deals every seed: the published replays were re-recorded, and the saved games in docs/ are
retired too — two of those were already dead before this release and nobody had noticed.

GITEA#6 — A TRAIN CARD IS NEVER DISCARDED, Timetabled and Extra alike. The forced play needed no
mechanism: nothing discardable plus a hand over the limit leaves exactly one legal way to end the
turn, and playing a train is unconditionally legal, so the corner cannot trap anyone. The bot
needed no rule either. 400/400 games finished, revenue unmoved, trains scheduled 1.2 -> 1.3. The
player is told on the card and on the button.

GITEA#7 — COACH COUNTS. 1/2 Crack Limited 3 -> 2, 5/6 The Sparrow 2 -> 3. A change to the cards,
so Trains3.pdf and the transcription keep the original numbers with a footnote while content.ts
and the Home Deck reference carry what the game plays.

CONTENT.TS COMMENT PASS — no data changed, only comments. Four were factually wrong, including an
office table naming counts doubled long ago and a pointer to a DEALT_DECK_SIZE that has never
existed. Every Enhancement row cited its implementation by line number and every citation had
rotted; they name functions now. Card counts came out of the comments, since they move with play
balance; source-sheet figures and dated measurements stayed.

TODO.md gains an item for a card reference generated from content.ts, in six sections, so the
documentation cannot disagree with the game.

715 tests pass, tsc clean, site builds.

src/sim/view.ts

@@ -18,7 +18,9 @@ import {
   laborersLeft,
   movesFor,
   ownCutFor,
+  isTrainCard,
   portersLeft,
+  resolveExtraStart,
   selectDestination,
 } from '../engine/apply.ts';
 import {
@@ -323,6 +325,14 @@ export type DivisionView = {
   /** Office nodes only: whose district this is. */
   /** Which SEAT's district this is — a position on the Division, not a player. */
   seat?: number;
+  /**
+   * Interchange only: trains standing in its yard, not out on the running line (state.ts).
+   *
+   * Separate from `trains` for the same reason `switching` is separate from an Office's A/D list —
+   * they are not occupying the thing whose capacity is being counted. An Extra made up here has to
+   * be VISIBLE, though, or the player who placed it has a train that exists nowhere on the map.
+   */
+  yard?: TrainChip[];
   /**
    * Office nodes only: crews working BELOW the Running Track.
    *
@@ -469,6 +479,15 @@ export type Frame = {
   hand: string[];
   /** What each hand card does, in the same order — names alone are not a playable hand. */
   handWhat: string[];
+  /**
+   * Whether each hand card may be DISCARDED, in the same order.
+   *
+   * §6.2 as ruled by Jesse (Gitea#6): a train card never can be. The player has to be told which
+   * cards those are, not merely find that a button is missing — that silence is the whole of the
+   * Gitea#2 complaint, where a blocked platform left the board with nothing to click and no reason.
+   * Named for the rule rather than for trains, since it answers the question the panel is asking.
+   */
+  handDiscardable: boolean[];
   deck: number;
   /** The face-up card on top of each Department pile — the only one that may be drawn. */
   departments: string[];
@@ -927,14 +946,29 @@ export function describeIntent(s: GameState, i: Intent): string {
       return `board passengers at ${at(i.at)}${onto(s, i.trayId, ' onto ')}`;
     case 'porter.detrain':
       return `detrain passengers at ${at(i.at)}${onto(s, i.trayId, ' from ')}`;
+    /**
+     * NAME THE PLACE AND THE DIRECTION, because the player is choosing both.
+     *
+     * This used to explain why the Extra had no choice — "it runs west, so that is the end it
+     * starts from". It has one now (§7, Jesse's ruling), and every candidate is on screen at once,
+     * so each label has to be distinguishable from its three or four siblings at a glance.
+     */
     case 'newTrain.startExtra': {
-      const runs = i.trainNumber % 2 === 0 ? 'east' : 'west';
-      if (i.atSeat === null) {
-        const end = i.trainNumber % 2 === 0 ? 'Western' : 'Eastern';
-        return `start Extra X${i.trainNumber} at the ${end} Division Point — it runs ${runs}, so that is the end it starts from`;
+      const where = resolveExtraStart(s, s.clock.currentActor ?? 0, i);
+      if (typeof where === 'string') return `start Extra X${i.trainNumber}`;
+      const { direction } = where;
+      if (where.at.kind === 'divisionPoint') {
+        const end = where.at.side === 'west' ? 'Western' : 'Eastern';
+        return `start Extra X${i.trainNumber} at the ${end} Division Point — it runs ${direction} from there`;
       }
-      const tier = officeProfile(areaAtSeat(s, i.atSeat).tier).name;
-      return `start Extra X${i.trainNumber} at the ${tier} in seat ${i.atSeat} — a Control Point, so it may begin its ${runs}bound run there instead`;
+      if (where.at.kind === 'mainline') {
+        return (
+          `start Extra X${i.trainNumber} ${direction}bound in the Interchange — it is made up in the ` +
+          'yard and highballs onto the Mainline once the Subdivision is clear'
+        );
+      }
+      const tier = officeProfile(areaAtSeat(s, where.at.seat).tier).name;
+      return `start Extra X${i.trainNumber} ${direction}bound at the ${tier} in seat ${where.at.seat} — a Control Point, so it may begin its run there`;
     }
 
     case 'newTrain.placeCar':
@@ -1159,6 +1193,9 @@ export function snapshot(
           };
         })],
         capacity: MAINLINE_PROFILES.find((m) => m.kind === n.card)?.trainsMayPass ? 2 : 1,
+        // Drawn at the start of the card: the yard is beside the rail, and this is the end the
+        // train will pull out of. It counts against nothing — see `yard` on DivisionView.
+        yard: (n.holding ?? []).map((id) => ({ ...trainChip(s, id), region: 0 })),
         modifiers: [
           ...(n.modifiers ?? []).map(prettyKey),
           ...(n.absSignals ? ['ABS Signals'] : []),
@@ -1247,6 +1284,7 @@ export function snapshot(
      */
     hand: [...(s.decks.hands.get(viewer) ?? [])].reverse().map((id) => cardName(s, id)),
     handWhat: [...(s.decks.hands.get(viewer) ?? [])].reverse().map((id) => cardDescription(s, id)),
+    handDiscardable: [...(s.decks.hands.get(viewer) ?? [])].reverse().map((id) => !isTrainCard(s, id)),
     deck: s.decks.homeOffice.length,
     departments: s.decks.departments.map((pile) => {
       const top = pile[pile.length - 1];