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/setup.test.ts

@@ -22,6 +22,7 @@ import {
   deckComposition,
   isFreightHouse,
   lengthProfile,
+  MAINLINE_DECK,
   mainlineCardCount,
   nextOfficeTier,
   officeProfile,
@@ -407,6 +408,42 @@ describe('game setup (component 2)', () => {
     }
   });
 
+  it('deals the Mainline cards from the printed deck, without replacement', () => {
+    /**
+     * `buildDivision` drew uniformly from the nine card TYPES with replacement, so a Division could
+     * be dealt two Interchanges (or two Tunnels), and Plains — printed twice in the deck — carried
+     * the same weight as cards printed once. That became a rules question rather than a flavour one
+     * when an Extra gained the right to start "at the Interchange if one is on the board" (§7): the
+     * board has to hold at most one for that to mean anything.
+     *
+     * Swept over many seeds because a single deal cannot tell a deck from a die.
+     */
+    const seen = new Map<string, number>();
+    for (let seed = 0; seed < 400; seed++) {
+      for (const players of [1, 2, 3, 4]) {
+        const g = createGame({
+          id: 'deck', seed,
+          config: players === 1 ? solitaireConfig : { ...solitaireConfig, mode: 'competitive' },
+          playerNames: Array.from({ length: players }, (_, i) => `P${i}`),
+        });
+        const cards = g.division.nodes.flatMap((n) => (n.kind === 'mainline' ? [n.card] : []));
+        assert.equal(cards.length, mainlineCardCount(players));
+        const counts = new Map<string, number>();
+        for (const c of cards) {
+          const n = (counts.get(c) ?? 0) + 1;
+          counts.set(c, n);
+          seen.set(c, (seen.get(c) ?? 0) + 1);
+          // Plains is the one card printed twice; nothing else may be dealt twice at all.
+          assert.ok(n <= (c === 'plains' ? 2 : 1), `${c} dealt ${n} times at seed ${seed}`);
+        }
+      }
+    }
+    // Every card in the deck reachable, so the deal is not quietly missing one.
+    for (const kind of new Set(MAINLINE_DECK)) {
+      assert.ok((seen.get(kind) ?? 0) > 0, `${kind} was never dealt in 400 seeds`);
+    }
+  });
+
   it('opens with the whole railroad as one Subdivision', () => {
     // §8 — every Office is a Whistle Post, which is not a Control Point.
     const g = newSolitaireGame();