feat: lighter air control (steer + stronger strafe) and 2-charge dash

- Air: direct steering bends existing velocity toward input without changing
  its magnitude (air_steer_rate), on top of Quake accelerate with raised
  gains (air_strafe_accel 55->90, per-tick cap 1.2->2.5). No-input air drag
  nearly removed so held momentum carries. Steering skips opposing input to
  avoid flipping through zero.
- Dash: charge system on the machine — dash_charges (2) spend instantly,
  each recharges in dash_cooldown (2 s). get_dash_cooldown_remaining() now
  reports time to the NEXT charge (0 while one is banked) so existing HUDs
  keep working; get_dash_charges() added for pips.
- Tests: dash tests updated to the charge API + new coverage for
  spend-2-then-recharge; 11/11 pass, spawn smoke clean.

Co-Authored-By: Claude Fable 5 <[email protected]>

movement/movement_state_machine.gd

@@ -48,7 +48,8 @@ var last_ground_time: float = 0.0
 var jump_buffer_time: float = 0.0
 var coyote_timer: float = 0.0
 var jump_cooldown_timer: float = 0.0
-var dash_cooldown_timer: float = 0.0
+var dash_charges: int = -1              # -1 = initialize from params on first tick
+var dash_recharge_timer: float = 0.0
 var current_jump_count: int = 0
 var chain_timer: float = 0.0
 var chain_count: int = 0
@@ -103,10 +104,18 @@ func _physics_process(delta: float) -> void:
 
 	# Update timers
 	jump_cooldown_timer = maxf(jump_cooldown_timer - delta, 0.0)
-	dash_cooldown_timer = maxf(dash_cooldown_timer - delta, 0.0)
 	slide_cooldown_timer = maxf(slide_cooldown_timer - delta, 0.0)
 	wall_cooldown_timer = maxf(wall_cooldown_timer - delta, 0.0)
 
+	# Dash charges: regain one per dash_cooldown while below max
+	if dash_charges < 0:
+		dash_charges = params.dash_charges
+	if dash_charges < params.dash_charges:
+		dash_recharge_timer -= delta
+		if dash_recharge_timer <= 0.0:
+			dash_charges += 1
+			dash_recharge_timer = params.dash_cooldown if dash_charges < params.dash_charges else 0.0
+
 	# Update chain timer
 	if chain_timer > 0.0 and on_ground:
 		chain_timer -= delta
@@ -401,5 +410,26 @@ func get_crouch_factor() -> float:
 		/ (original_capsule_height * 0.5), 0.0, 1.0)
 
 
+func can_dash() -> bool:
+	return dash_charges != 0  # -1 (uninitialized) counts as ready
+
+
+## Spend one dash charge and start the recharge clock if it isn't running.
+func consume_dash_charge() -> void:
+	if dash_charges < 0:
+		dash_charges = params.dash_charges
+	dash_charges = maxi(dash_charges - 1, 0)
+	if dash_recharge_timer <= 0.0:
+		dash_recharge_timer = params.dash_cooldown
+
+
+## Seconds until the NEXT dash is available (0 when a charge is banked).
+## HUDs also read get_dash_charges() to draw pips.
 func get_dash_cooldown_remaining() -> float:
-	return dash_cooldown_timer
+	if dash_charges != 0:
+		return 0.0
+	return maxf(dash_recharge_timer, 0.0)
+
+
+func get_dash_charges() -> int:
+	return dash_charges if dash_charges >= 0 else params.dash_charges