feat(combat): use fly speed for movement

Movement budget is now max(land, fly) speed. Updates the harvie golden: Harvie (land 10 / fly 80) is a flyer and now flies at 80 ft, so he wins vs the goblin instead of being pinned crawling at 10 ft.

src/pf1e_simulator/combat.py

@@ -34,6 +34,8 @@ Phase 0 documented deviations from PF1e (conventions):
 - Movement: a move action travels up to the combatant's speed in cells along
   the true shortest path (Dijkstra cost field from the target, 5-10-5
   diagonals), stopping adjacent to the nearest enemy; ties keep delta order.
+  The speed budget is the best of land and fly speed (V4); flying over
+  obstacles or difficult terrain is NOT modeled (grid costs still apply).
 - Line of effect gates all attacks: a target fully behind blocking terrain
   cannot be attacked, and the policy moves to gain sight instead.
 - Cover (corner rule) grants +4 AC on hit and crit-confirm rolls; melee and
@@ -158,7 +160,7 @@ _FIGHT_DEFENSIVELY_AC_BONUS = 2  # PF1e: fighting defensively grants +2 dodge AC
 _FIGHT_DEFENSIVELY_ATTACK_PENALTY = -4  # PF1e: and -4 on attacks / crit confirms
 _AID_ANOTHER_DC = 10  # PF1e: aid another is an attack roll against AC 10
 _AID_ANOTHER_BONUS = 2  # PF1e: a successful aid grants +2 (next attack or AC)
-_RUN_SPEED_FACTOR = 4  # PF1e: running is a full-round action at 4x land speed
+_RUN_SPEED_FACTOR = 4  # PF1e: running is a full-round action at 4x speed
 _SAVE_DESCRIPTOR_CONDITIONS = frozenset({
     "fear", "cold", "electricity", "fey", "divination", "poison", "disease",
     "mind_affecting",
@@ -312,6 +314,18 @@ def _effective_reach_ft(state: CombatantState, weapon: AttackSpec) -> int:
     return max(_SIZE_NATURAL_REACH_FT.get(state.combatant.size, 5), weapon.reach_ft)
 
 
+def _speed_ft(state: CombatantState) -> int:
+    """Movement budget in feet: the best of the combatant's land and fly speed.
+
+    Simplification (V4): a creature that has a fly speed is assumed to use it;
+    flying OVER obstacles or difficult terrain is NOT modeled — the grid's
+    passability and terrain costs still apply to the whole budget. No
+    fly maneuverability, no 3D flight. Swim/climb/burrow speeds do not exist
+    in the model (fly only).
+    """
+    return max(state.combatant.speed_land_ft, state.combatant.speed_fly_ft or 0)
+
+
 def _bresenham_line(start: Pos, end: Pos) -> list[Pos]:
     """Integer Bresenham line from start to end (exclusive of start, inclusive of end)."""
     r0, c0 = start
@@ -1081,6 +1095,7 @@ class CombatEngine:
             ),
             "speed_land_ft": state.combatant.speed_land_ft,
             "speed_fly_ft": state.combatant.speed_fly_ft,
+            "speed_effective_ft": _speed_ft(state),
             "ac": {
                 "total": state.combatant.ac.total,
                 "touch": state.combatant.ac.touch,
@@ -2336,15 +2351,15 @@ class CombatEngine:
         (API publique, lecture pour politique LLM.) Uses the same cost model as
         ``_move_path``: a full Dijkstra field from the target's anchor (other
         active states' cells blocked), then the cheapest field value over
-        ``state``'s footprint, compared against the combatant's land speed.
-        Read-only: never mutates state nor consumes RNG.
+        ``state``'s footprint, compared against the combatant's effective
+        (land-or-fly) speed. Read-only: never mutates state nor consumes RNG.
         """
         blocked = self._blocked(state, target)
         field = self._grid.reachable(target.pos, None, blocked)
         cost_cells = self._footprint_cost(state.occupied_cells(), field)
         if cost_cells is None:
             return None
-        speed_cells = state.combatant.speed_land_ft // _SQUARE_FT
+        speed_cells = _speed_ft(state) // _SQUARE_FT
         if cost_cells > speed_cells:
             return None
         return cost_cells * _SQUARE_FT
@@ -2495,7 +2510,7 @@ class CombatEngine:
             self._grid, state.occupied_cells(), target.occupied_cells()
         ):
             return ChargeResult(weapon=None, distance_ft=0, reason="no_line_of_effect")
-        speed_cells = state.combatant.speed_land_ft // _SQUARE_FT
+        speed_cells = _speed_ft(state) // _SQUARE_FT
         max_cells = 2 * speed_cells
         blocked = self._blocked(state, target)
         melee_weapons = [w for w in state.usable_attacks() if w.kind == "melee"]
@@ -2603,7 +2618,7 @@ class CombatEngine:
         """
         reach_cells = _effective_reach_ft(attacker, weapon) // _SQUARE_FT
         min_reach_cells = weapon.reach_ft // _SQUARE_FT if weapon.reach_ft > _SQUARE_FT else 0
-        speed_cells = attacker.combatant.speed_land_ft // _SQUARE_FT
+        speed_cells = _speed_ft(attacker) // _SQUARE_FT
         max_cells = 2 * speed_cells
         blocked = self._blocked(attacker, target)
         end = self._charge_end(
@@ -4804,7 +4819,7 @@ class CombatEngine:
         ``speed_factor`` widens the budget (run: 4x speed, U5e).
         """
         speed_cells = int(
-            state.combatant.speed_land_ft
+            _speed_ft(state)
             // _SQUARE_FT
             * self._get_speed_mult(state)
             * speed_factor
@@ -4850,7 +4865,7 @@ class CombatEngine:
         """
         speed_mult = self._get_speed_mult(state)
         speed_cells = int(
-            state.combatant.speed_land_ft
+            _speed_ft(state)
             // _SQUARE_FT
             * speed_mult
             * speed_factor
@@ -4910,7 +4925,7 @@ class CombatEngine:
         step that maximizes distance (cost) from the threat each cell.
         """
         speed_mult = self._get_speed_mult(state)
-        max_cells = int(2 * (state.combatant.speed_land_ft // _SQUARE_FT) * speed_mult)
+        max_cells = int(2 * (_speed_ft(state) // _SQUARE_FT) * speed_mult)
         if max_cells <= 0:
             return []
         blocked = self._blocked(state)