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/10-spellgrid/reference/rust/src/engine/puzzle/movement.rs

@@ -59,18 +59,22 @@ pub struct Plan {
     pub destroyed: BTreeSet<ObjectId>,
 }
 
-/// 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.
 pub struct Planner<'a> {
     level: &'a Level,
     dir: Dir,
+    stepped: &'a BTreeSet<ObjectId>,
     plan: Plan,
 }
 
 impl<'a> Planner<'a> {
-    pub fn new(level: &'a Level, dir: Dir) -> Planner<'a> {
+    pub fn new(level: &'a Level, dir: Dir, stepped: &'a BTreeSet<ObjectId>) -> Planner<'a> {
         Planner {
             level,
             dir,
+            stepped,
             plan: Plan::default(),
         }
     }
@@ -100,11 +104,16 @@ impl<'a> Planner<'a> {
     /// 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.
     pub fn try_move(&mut self, id: ObjectId) -> bool {
         if self.plan.moving.contains(&id) || self.plan.destroyed.contains(&id) {
             return true;
         }
+        if self.stepped.contains(&id) {
+            return false;
+        }
         let level = self.level;
         let o = level.board().get(id);
         let (dx, dy) = self.dir.delta();