feat(rules): allow a move action in place of a standard action

PF1e CRB (Actions in Combat): a move action can be taken instead of the
standard one. The budget filter now converts a second move action onto
the standard slot when the move slot is spent and the standard is still
free, so (move, stand_up) and (move, move) are legal; a third move (or
any further standard) is still surplus. The greedy walk is expressed
with a spent-slot map to stay inside the C901 complexity ceiling.

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

README.md

@@ -360,7 +360,11 @@ Règles modélisées :
   compartiment du budget — standard, mouvement, swift, round complet, ou
   libre/conditionnel (hors budget) — et la séquence est vérifiée contre le budget
   (≤ 1 standard **ou** 1 round complet, ≤ 1 mouvement, ≤ 1 swift ; un round
-  complet consacre à la fois le standard ET le mouvement). La dégradation est
+  complet consacre à la fois le standard ET le mouvement). **Conversion
+  standard → mouvement** (CRB : une action de mouvement peut se prendre « à la
+  place » de l'action standard) : quand le compartiment mouvement est déjà
+  occupé et que le standard est encore libre, un second mouvement consomme le
+  standard — `(move, stand_up)` et `(move, move)` sont donc légaux. La dégradation est
   **déterministe et stable en ordre** : parcours glouton dans l'ordre, chaque
   action est gardée tant que son compartiment est libre ; le résultat est donc le
   plus préfixe-sous-séquence légal, et toute action excédentaire est retirée et

src/pf1e_simulator/combat.py

@@ -5900,32 +5900,38 @@ def _action_economy_filter(actions: tuple[Action, ...]) -> tuple[Action, ...]:
     Greedy in-order walk: each action is kept while its budget slot is free
     (one standard, one move, one swift; a full-round action is only legal
     while BOTH the standard and the move slot are still free and consumes
-    them all). The kept sequence is therefore the earliest order-stable legal
+    them all). PF1e (CRB, "Actions in Combat"): a move action can be taken
+    "instead of" the standard one — when the move slot is already spent and
+    the standard slot is still free, a further move action converts the
+    standard slot (so (move, stand_up) and (move, move) are legal). The kept
+    sequence is therefore the earliest order-stable legal
     prefix-subsequence; every skipped action is deterministic.
     """
     kept: list[Action] = []
-    standard_used = False
-    move_used = False
-    swift_used = False
+    spent: dict[_ActionEconomySlot, bool] = {
+        "standard": False,
+        "move": False,
+        "swift": False,
+        "full_round": False,
+        "free": False,
+    }
     for action in actions:
         slot = _action_economy_slot(action.kind)
-        if slot == "standard":
-            if standard_used:
+        if slot == "free":
+            kept.append(action)
+            continue
+        if slot == "full_round":
+            if spent["standard"] or spent["move"]:
                 continue
-            standard_used = True
-        elif slot == "move":
-            if move_used:
-                continue
-            move_used = True
-        elif slot == "swift":
-            if swift_used:
-                continue
-            swift_used = True
-        elif slot == "full_round":
-            if standard_used or move_used:
-                continue
-            standard_used = True
-            move_used = True
+            spent["standard"] = True
+            spent["move"] = True
+            kept.append(action)
+            continue
+        if slot == "move" and spent["move"]:
+            slot = "standard"  # conversion: a move action consumes the standard slot
+        if spent[slot]:
+            continue
+        spent[slot] = True
         kept.append(action)
     return tuple(kept)
 

tests/test_conformance_action_economy.py

@@ -144,9 +144,19 @@ def test_legal_sequences_are_kept_unchanged() -> None:
 
 
 def test_two_moves_conflict_but_free_steps_do_not() -> None:
-    # stand_up is a move action: a second move is surplus.
+    # PF1e conversion: a move action taken while the move slot is spent
+    # consumes the standard slot instead — two moves are legal, so
+    # (move, stand_up) is kept whole.
     actions = (_foe("move"), _foe("stand_up"))
-    assert _action_economy_filter(actions) == (_foe("move"),)
+    assert _action_economy_filter(actions) == actions
+    moves = (_foe("move"), _foe("move"))
+    assert _action_economy_filter(moves) == moves
+    # The third move has neither slot left: standard and move both spent.
+    assert _action_economy_filter((*moves, _foe("attack"))) == moves
+    assert _action_economy_filter((*moves, _foe("full_attack"))) == moves
+    # run is full-round: it cannot follow a move (both slots needed upfront).
+    assert _action_economy_filter((_foe("move"), _foe("run"))) == (_foe("move"),)
+    assert _action_economy_filter((_foe("run"), _foe("move"))) == (_foe("run"),)
     # 5foot_step is free: two steps do not consume the move slot.
     steps = (_foe("5foot_step"), _foe("5foot_step"))
     assert _action_economy_filter(steps) == steps