fix(rules): apply maneuver failure consequences

PF1e (SRD Trip): "If your attack fails by 10 or more, you are knocked prone instead" - a trip whose total lands at CMD-10 or below now knocks the attacker prone (1 round). PF1e (SRD Overrun): "If your overrun attempt fails, you stop in the space directly in front of the opponent, or the nearest open space in front of the creature" - a failed overrun from beyond adjacency walks the attacker to the free approach cell nearest the target; an already-adjacent attacker stays put. README updated.

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

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

src/pf1e_simulator/combat.py

@@ -261,6 +261,7 @@ _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 speed
 _OVERRUN_PRONE_MARGIN = 5  # PF1e: overrun knocks prone only on a 5+ CMB margin
 _BULL_RUSH_EXTRA_PER_MARGIN = 5  # PF1e: +5 ft push per 5 points above CMD
+_TRIP_RETALIATION_MARGIN = 10  # PF1e: trip failing by 10+ knocks the attacker prone
 _SAVE_DESCRIPTOR_CONDITIONS = frozenset({
     "fear", "cold", "electricity", "fey", "divination", "poison", "disease",
     "mind_affecting",
@@ -4119,6 +4120,20 @@ class CombatEngine:
     ) -> None:
         if not m.success:
             self._maneuver_fail(state, target, "trip", m)
+            # PF1e (SRD Trip): "If your attack fails by 10 or more, you are
+            # knocked prone instead."
+            if m.total <= m.target_cmd - _TRIP_RETALIATION_MARGIN:
+                state.active_conditions.append(
+                    ActiveCondition(
+                        condition=CONDITIONS_BY_NAME["prone"],
+                        rounds_left=1,
+                        source="maneuver: trip retaliation",
+                    )
+                )
+                self._log(
+                    f"round {self._current_round} {state.combatant.id}: "
+                    f"trip backfire -> attacker prone"
+                )
             return
         target.active_conditions.append(
             ActiveCondition(
@@ -4264,6 +4279,7 @@ class CombatEngine:
     ) -> None:
         if not m.success:
             self._maneuver_fail(state, target, "overrun", m)
+            self._overrun_fail_stop(state, target)
             return
         # PF1e (CRB "Overrun"): a successful maneuver moves you through the
         # target's square; the target is knocked prone only if the attack
@@ -4293,6 +4309,35 @@ class CombatEngine:
             f"CMD {m.target_cmd} -> {outcome}"
         )
 
+    def _overrun_fail_stop(
+        self, state: CombatantState, target: CombatantState
+    ) -> None:
+        """Park a failed overrun on the open approach cell in front of the target.
+
+        PF1e (SRD Overrun): "If your overrun attempt fails, you stop in the
+        space directly in front of the opponent, or the nearest open space
+        in front of the creature if there are other creatures occupying that
+        space." An already-adjacent attacker is in front: no move, no log.
+        """
+        ar, ac = state.pos
+        tr, tc = target.pos
+        steps = max(abs(tr - ar), abs(tc - ac))
+        if steps <= 1:
+            return
+        dr = 1 if tr - ar > 0 else (-1 if tr - ar < 0 else 0)
+        dc = 1 if tc - ac > 0 else (-1 if tc - ac < 0 else 0)
+        for i in range(steps - 1, 0, -1):
+            cell = (ar + dr * i, ac + dc * i)
+            if self._cells_free(self._footprint_at(cell, state), state):
+                start = state.pos
+                state.pos = cell
+                self._log(
+                    f"round {self._current_round} {state.combatant.id}: "
+                    f"overrun blocked, stopped ({start[0]},{start[1]})->"
+                    f"({cell[0]},{cell[1]})"
+                )
+                return
+
     def _maneuver_dirty_trick(
         self,
         state: CombatantState,