make turnout description more clear. fix curves from breaking running track.

CHANGELOG.md

@@ -10,6 +10,47 @@ The target is 20 Revenue over 5 Days.
 
 ## Unreleased
 
+### Turnouts say what they do, and a curve may not break the Running Track
+
+**"Right-hand turnout, stem east, through west, diverges north at 45°"** is three pieces of jargon
+and a compass reading, and none of it answers the only question being asked: *if my train comes in
+from over there, where can it go?* Turnouts now read
+
+> allows traffic from the east to travel west or turn to the south
+
+and curves
+
+> carries traffic from the west round to the south
+
+everywhere they appear — on the card in hand, on the placement it would make, and on the card once it
+is down. §A.1's rule falls out of the same sentence rather than needing a shouty clause of its own:
+a train coming the other way, from the through end or the diverging one, may only leave by the stem,
+so the two roads never join.
+
+**A curve laid in the Running Track dead-ends the main.** A curve has ONE road — from an east or west
+edge round to its 45° leg — so a card of it standing in the running row stops the through route at
+that square and cuts the Office off from its own Limits. Nothing forbade it, and the bot did it: an
+early trace shows it laying a `ne` curve at (0,−1), turning the west end of its own Running Track
+into a stub. Every card that may stand in that row now has to carry the road across it —
+`carriesThroughTrack` — which straights, turnouts, Limits signs, the Office and industries all do.
+Reported as `BREAKS_RUNNING_TRACK` rather than `NOT_CONNECTED`, because it is a different mistake:
+the card would join perfectly well and would still leave the main stopping dead at it.
+
+**The crossover is confirmed, both hands.** A turnout that *"allows traffic from the east to travel
+west or turn to the south"* joins the one directly beneath it that *"allows traffic from the west to
+travel east or turn to the north"* — the two 45° legs are one continuous rail across the card edge.
+It already worked; it now has a test that says so in those words, along with its mirror built from
+the other hand, the mismatched pair that must NOT join, and a crew actually running down through it
+onto the parallel track.
+
+**Measured, and worth flagging:** barring curves from the running row cost the bot a good deal —
+districts 28.0 → 19.7 cards, facilities 2.23 → 1.85, revenue about 2.0 → 0.8. The rule is right and
+the bot was partly living off an illegal placement. Two tests needed widening rather than weakening
+as a result: the unload regression sampled three deals and now samples twelve (unloads still happen,
+34 across a 40-deal sweep, just not on those three), and the canvas bounds test now holds a straight
+as well as a curve, since a curve alone is offered only one square once the running row is closed to
+it.
+
 ### The Crew Tray is a train, and a train must be made up to leave
 
 **§8.2 was not checked at all.** A train could highball onto the Mainline engine-last with its