fix(puzzle): an object steps once per movement phase; negated conversion is settled per object

Bug 1 (modules 08-10): a YOU object pulled by an earlier mover took a second step of its own. Level movement now keeps the ids that stepped in a committed plan this phase; such a YOU object starts no move, and Planner try_move answers no for it. Regression: test_08x_pulled_you_moves_once (Module 8 Expansion Drop).

Bug 2 (modules 09-10): convert honoured negation only per rule, so ALL IS ROCK beat BABA IS NOT ROCK. A target Y is now skipped for an object if any active negated rule IS NOT Y names it. Module 9 and 10 references (and their drop solutions) now carry ALL, the Module 7 Expansion Drop. Regression: test_09_negated_conversion_beats_group.

Co-Authored-By: Claude Fable 5.2 <noreply@anthropic.com>

course/08-push-chains/reference/ts/src/engine/puzzle/movement.ts

@@ -63,13 +63,18 @@ export interface MoveContext {
   responses(): readonly Response[];
 }
 
-/** Plans one move on a board it only reads. */
+/**
+ * Plans one move on a board it only reads. `stepped` holds the objects that have
+ * already stepped in this movement phase, in an earlier committed plan: an object
+ * steps at most once per phase, so none of them can step again.
+ */
 export class Planner {
   private plan: Plan = { moving: new Set(), destroyed: new Set() };
 
   constructor(
     private readonly level: MoveContext,
     private readonly dir: Dir,
+    private readonly stepped: ReadonlySet<ObjectId>,
   ) {}
 
   /** Does object `id` have `property`, under the rules in force before the move? */
@@ -98,10 +103,13 @@ export class Planner {
    * Plan object `id` stepping one tile in the move's direction, with whatever
    * the responses add. Returns whether it can. If it can't, the plan is left as
    * it was before the call. An object already planned to move, or to be
-   * destroyed, is out of the way: the answer is yes, and nothing is added.
+   * destroyed, is out of the way: the answer is yes, and nothing is added. An
+   * object that has already stepped in this movement phase can't step again: the
+   * answer is no.
    */
   tryMove(id: ObjectId): boolean {
     if (this.plan.moving.has(id) || this.plan.destroyed.has(id)) return true;
+    if (this.stepped.has(id)) return false;
     const o = this.level.board.get(id);
     const [dx, dy] = delta(this.dir);
     const to: Pos = [o.x + dx, o.y + dy];