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>

tests/test_maneuvers.py

@@ -194,6 +194,60 @@ def test_bull_rush_natural_20_below_cmd_pushes_one_cell() -> None:
     assert b.pos == (1, 3)
 
 
+def test_trip_fails_by_10_knocks_attacker_prone() -> None:
+    # SRD Trip: "If your attack fails by 10 or more, you are knocked prone
+    # instead." b CMD 30 (bab 20); a total 10+2=12 fails by 18.
+    a = make_state(make_combatant("a", attack_bonus=2), "players", (1, 1))
+    b = make_state(make_combatant("b", attack_bonus=20), "monsters", (1, 2))
+    engine = make_engine([1, 10], [a, b])
+    engine._execute_maneuver(a, b, "trip")
+    assert not any(c.condition.name == "prone" for c in b.active_conditions)
+    prone = next(c for c in a.active_conditions if c.condition.name == "prone")
+    assert prone.source == "maneuver: trip retaliation"
+
+
+def test_trip_fails_by_less_than_10_attacker_stands() -> None:
+    # a total 19+2=21 vs CMD 30 fails by 9 — no retaliation.
+    a = make_state(make_combatant("a", attack_bonus=2), "players", (1, 1))
+    b = make_state(make_combatant("b", attack_bonus=20), "monsters", (1, 2))
+    engine = make_engine([1, 19], [a, b])
+    engine._execute_maneuver(a, b, "trip")
+    assert not any(c.condition.name == "prone" for c in a.active_conditions)
+
+
+def test_overrun_fail_stops_in_front_of_target() -> None:
+    # SRD Overrun: "If your overrun attempt fails, you stop in the space
+    # directly in front of the opponent." a at (1,0), b at (1,3): the failed
+    # attempt parks a on (1,2), the cell in front of b. a is not threatened
+    # from (1,0), so no AoO roll is consumed: the single d20 is the maneuver.
+    a = make_state(make_combatant("a", attack_bonus=2), "players", (1, 0))
+    b = make_state(make_combatant("b"), "monsters", (1, 3))
+    engine = make_engine([5], [a, b])
+    engine._execute_maneuver(a, b, "overrun")
+    assert a.pos == (1, 2)
+
+
+def test_overrun_fail_nearest_open_when_front_occupied() -> None:
+    # "...or the nearest open space in front of the creature if there are
+    # other creatures occupying that space." Blocker on (1,2): a stops (1,1).
+    a = make_state(make_combatant("a", attack_bonus=2), "players", (1, 0))
+    b = make_state(make_combatant("b"), "monsters", (1, 3))
+    c = make_state(make_combatant("c"), "monsters", (1, 2))
+    engine = make_engine([1, 5], [a, b, c])
+    engine._execute_maneuver(a, b, "overrun")
+    assert a.pos == (1, 1)
+
+
+def test_overrun_fail_adjacent_attacker_does_not_move() -> None:
+    # An already-adjacent attacker is in front of the target: it stays put.
+    a = make_state(make_combatant("a", attack_bonus=2), "players", (1, 1))
+    b = make_state(make_combatant("b"), "monsters", (1, 2))
+    engine = make_engine([1, 5], [a, b])
+    engine._execute_maneuver(a, b, "overrun")
+    assert a.pos == (1, 1)
+    assert not any("overrun blocked" in line for line in engine._transcript)
+
+
 def test_overrun_knocks_prone_and_moves_through() -> None:
     # d20=15+2=17 vs CMD 12: margin 5 -> prone AND moved through (CRB
     # "Overrun": prone only when the attack exceeds CMD by 5 or more).