Fix parking trains, freight deadlock, and Whistle Post lock-in

src/engine/intents.ts

@@ -34,9 +34,8 @@ export type Intent =
   /**
    * Lay a piece from your personal track supply (§12.2 / content.ts TRACK_SUPPLY).
    *
-   * ASSUMPTION, flagged: the design moves track out of the deck into a per-player supply but does
-   * not say when you may lay it. Treated as a play available during the "draw a card" option,
-   * matching how track behaved when it WAS a card. See implications.md §10 Q10.
+   * Laid during the "draw a card" option, one piece a turn — how track behaved when it WAS a card.
+   * Confirmed; see implications.md §10 Q10.
    */
   | { type: 'track.lay'; geometry: TrackGeometry; hand: Hand; placement: GridCoord; variant?: number }
   | { type: 'draw.end' }