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.

test/apply.test.ts

@@ -7,6 +7,7 @@ import { describe, it } from 'node:test';
 import assert from 'node:assert/strict';
 
 import { applyIntent, check, areaOf, facilityCarTypes, movesFor, reduce } from '../src/engine/apply.ts';
+import { pump } from '../src/engine/advance.ts';
 import { HAND_LIMIT, INDUSTRY_PROFILES, MAX_CONSIST, MOVES_PER_LOCAL_OPS, officeProfile } from '../src/engine/content.ts';
 import type { Intent } from '../src/engine/intents.ts';
 import { legalActions } from '../src/engine/legal.ts';
@@ -261,6 +262,122 @@ describe('Local Operations: drawing (§6.2)', () => {
     assert.equal(check(s, 0, { type: 'draw.end' }), null, 'the turn cannot be ended even at the limit');
   });
 
+  describe('a train card is never discarded (Gitea#6)', () => {
+    /**
+     * Jesse's ruling, v0.4.9e playtest: "Players are not allowed to discard Train cards. They may
+     * keep the card in their hand for multiple stages and even multiple days, but they may not
+     * discard it. If a player has three train cards in their hand, and they draw a fourth, then they
+     * must play one of those cards."
+     *
+     * Extras count too — an Extra is a train, even though it runs once and ends in the Salvage Yard
+     * where a Timetabled card joins the timetable for the rest of the game.
+     *
+     * Note there is no new FORCING mechanism, and deliberately so: the corner is what the two
+     * existing rules produce together. Nothing discardable plus "you may not end the turn over the
+     * limit" leaves exactly one legal way on, and playing a train is unconditionally legal.
+     */
+    const handOf = (s: GameState, kinds: string[]): string[] => {
+      // Hand-pick cards of the wanted kinds straight out of the catalogue, so the test does not
+      // depend on what the shuffle happened to deal.
+      const picked: string[] = [];
+      for (const want of kinds) {
+        for (const [id, card] of s.cards) {
+          if (card.kind.kind !== want || picked.includes(id)) continue;
+          picked.push(id);
+          break;
+        }
+      }
+      assert.equal(picked.length, kinds.length, 'the catalogue is missing a card this test needs');
+      s.decks.hands.set(0, picked);
+      return picked;
+    };
+
+    it('refuses the discard, for a Timetabled train and for an Extra alike', () => {
+      const s = game();
+      applyIntent(s, 0, { type: 'localOps.choose', option: 'draw' });
+      const [timetabled, extra, track] = handOf(s, ['timetabledTrain', 'extraTrain', 'track']);
+      assert.equal(
+        check(s, 0, { type: 'card.discard', cardId: timetabled!, toSlot: 0 }),
+        'TRAINS_ARE_NEVER_DISCARDED',
+      );
+      assert.equal(
+        check(s, 0, { type: 'card.discard', cardId: extra!, toSlot: 0 }),
+        'TRAINS_ARE_NEVER_DISCARDED',
+      );
+      // And everything else is still discardable — the rule is about trains, not about discarding.
+      assert.equal(check(s, 0, { type: 'card.discard', cardId: track!, toSlot: 0 }), null);
+    });
+
+    it('never offers the discard, so the bot needs no rule of its own', () => {
+      const s = game();
+      applyIntent(s, 0, { type: 'localOps.choose', option: 'draw' });
+      const [timetabled] = handOf(s, ['timetabledTrain', 'track']);
+      const offered = legalActions(s, 0).filter(
+        (i) => i.type === 'card.discard' && i.cardId === timetabled,
+      );
+      assert.deepEqual(offered, [], 'a train discard was offered as a legal action');
+    });
+
+    it('leaves PLAYING a train as the only way out of a hand of four trains', () => {
+      const s = game();
+      applyIntent(s, 0, { type: 'localOps.choose', option: 'draw' });
+      const four = handOf(s, ['timetabledTrain', 'timetabledTrain', 'timetabledTrain', 'extraTrain']);
+      assert.ok(four.length > HAND_LIMIT, 'this test needs a hand over the limit');
+
+      // Over the limit, so the turn cannot be ended...
+      assert.equal(check(s, 0, { type: 'draw.end' }), 'HAND_LIMIT');
+      // ...and not one of them may be discarded...
+      for (const id of four) {
+        assert.equal(check(s, 0, { type: 'card.discard', cardId: id, toSlot: 0 }), 'TRAINS_ARE_NEVER_DISCARDED');
+      }
+      // ...but playing one is always legal, so the player is never actually stuck.
+      assert.equal(check(s, 0, { type: 'card.play', cardId: four[0]! }), null);
+      assert.ok(applyIntent(s, 0, { type: 'card.play', cardId: four[0]! }).ok);
+      assert.equal(s.decks.hands.get(0)!.length, HAND_LIMIT);
+      assert.equal(check(s, 0, { type: 'draw.end' }), null, 'playing a train did not free the turn');
+    });
+
+    it('lets a train be held across Stages and into the next Day', () => {
+      // "They may keep the card in their hand for multiple stages and even multiple days." Nothing
+      // sweeps a hand at a Stage or Day boundary, and this is what says so out loud.
+      const s = game();
+      const [timetabled] = handOf(s, ['timetabledTrain', 'track']);
+      const startDay = s.clock.day;
+
+      // Play out Stages by taking whatever ends the current turn, until the Day turns over.
+      for (let guard = 0; guard < 400 && s.clock.day === startDay; guard++) {
+        pump(s);
+        const actor = s.clock.currentActor;
+        if (actor === null) break;
+        const options = legalActions(s, actor);
+        const end = options.find((i) => i.type.endsWith('.end')) ?? options[0];
+        if (!end) break;
+        applyIntent(s, actor, end);
+      }
+
+      assert.ok(s.clock.day > startDay, `the Day never turned (stopped at ${s.clock.day}/${s.clock.stage})`);
+      assert.ok(
+        (s.decks.hands.get(0) ?? []).includes(timetabled!),
+        'the train did not survive being held into the next Day',
+      );
+      assert.equal(
+        check(s, 0, { type: 'card.discard', cardId: timetabled!, toSlot: 0 }),
+        'TRAINS_ARE_NEVER_DISCARDED',
+        'a Day boundary made a train discardable',
+      );
+    });
+
+    it('tells the player on the card itself, and on the button when every card is a train', () => {
+      // The Gitea#2 lesson: a rule the player cannot see is a board with nothing to click and no
+      // reason given.
+      const s = game();
+      handOf(s, ['timetabledTrain', 'extraTrain', 'track']);
+      const f = snapshot(s, [], null);
+      // `hand` is reversed for display, so compare as a set rather than by position.
+      assert.deepEqual([...f.handDiscardable].sort(), [false, false, true]);
+    });
+  });
+
   it('discards face up ON TOP of a chosen Department, burying what was there', () => {
     // The choice of WHICH Department is the strategy: a card put on an empty-ish pile is an offer, a
     // card put on top of one a rival wants takes that card out of reach. Overwriting the slot — what