v0.4.9f — an Extra starts where you put it, a train card is never discarded

The 0.6.2 change, ported to the playtest line. Three from the v0.4.9e gameplay-testing round —
Gitea#4 extras did not start where the player said, #6 train cards could be discarded, #7 four
train cards had the wrong coach counts — plus two bugs found underneath #4. Gitea#2 is diagnosed
but NOT fixed; it needs a ruling, and the reasoning is in TODO.md.

GITEA#4 — AN EXTRA STARTS WHERE THE PLAYER PUTS IT. Both Division Points are offered now, and the
START decides the direction rather than the number: an odd westbound Extra placed at the WEST end
would otherwise leave the Division on its first move having crossed nothing and be paid for the
run. 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 an
Extra there can never force a collision, a guaranteed one holds it for another Stage, and a
potential one is the Superintendent's to rule on, which are §8.1's two existing answers. Where an
Extra may start is a new setting in the New Game dialog, defaulting to what the engine already did
so this build does not change under its testers mid-line.

FOUND UNDERNEATH IT, both already shipping: an Extra started away from a Division Point could
never be given a consist and ran empty, so the Control Point start has been broken since it was
added; and collide left destroyed trains' transits on the Mainline card, permanently poisoning
that card for every later train.

THE MAINLINE CARDS ARE DEALT FROM THE PRINTED DECK NOW, without replacement. They were drawn from
the nine types with replacement, so a Division could hold two Interchanges — and "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. This re-deals every seed, so both published replays were retired and re-recorded.

GITEA#6 — A TRAIN CARD IS NEVER DISCARDED, Timetabled and Extra alike. No forcing mechanism was
needed: 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 a hand of four cannot trap anyone. The hand
panel says so on the train, and the blocked end-turn button changes its wording.

GITEA#7 — COACH COUNTS. 1/2 Crack Limited 3 -> 2, 5/6 The Sparrow 2 -> 3.

WHAT DIFFERS FROM THE MAIN LINE. The car-placement round rotation test that accompanies #7 there
arrived with the 0.6 multiplayer work and does not exist here, so there was nothing for the
coach-count change to follow. src/web/main.ts and test/web.test.ts needed hand-resolution: this
line's New Game dialog has neither the mode radios nor the victory dials, so only the Extra-start
parts were taken. The content.ts comment pass came across whole; main's TODO documentation item
did not, since this line keeps its own TODO.

623 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';
@@ -259,6 +260,122 @@ 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