fix(combat): Thread 5-10-5 diagonal parity through all budget-consuming paths

The greedy move/run/flee/charge descent helpers hardcoded diagonal parity 0,
letting a speed-30 walker cover 6 diagonal cells (cell-count budget). Under
5-10-5 (SRD Movement, Tactical) the same walker covers only 4 cells
(1+2+1+2=6 squares).

Threading the running diagonal count:
- _best_move_step / _best_flee_step: accept diagonals_used param
- _descend_path / _run_line_path / _flee_path: track and pass parity
- _charge_end: use _path_cost_5105() instead of len(path) for max check
- _path_cost_5105: new helper; computes total 5-10-5 cost of any path

Updated golden paths in test_aoo_limit_one_per_round (5-cell path now
takes an orthogonal detour to avoid expensive 2nd diagonal), test_run_*
 (speed-30 diagonal move stops at 4 cells), and staggered_withdraw
(single-speed diagonal withdraw stops at 4 cells).

tests/test_aid_and_run.py

@@ -358,7 +358,9 @@ def test_run_toward_target_outreaches_normal_move() -> None:
     )
     eng2.run()
     move_hero = eng2._states[0]
-    assert move_hero.pos == (6, 6)  # only 6 cells of the 15-cell path
+    # 5-10-5: 4 diagonal cells cost 1+2+1+2 = 6 = the speed budget; the old
+    # cell-count budget let a speed-30 walker cover 6 diagonal cells.
+    assert move_hero.pos == (4, 4)  # only 4 diagonal cells of the 15-cell path
     assert grid.distance(run_hero.pos, foe.pos) < grid.distance(move_hero.pos, foe2.pos)