feat(movement): add movement state machine with air/ground/wallrun/slide/dash/ground states

- MovementStateMachine: core state machine base
- MovementParams: export-rich tunable resource
- StateGround/StateAir: grounded & aeriel locomotion with coyote, buffered jump, bunny hop
- StateWallRun / StateWallCling: wall-based traversal with wall-jump off
- StateSlide: sprint-parallel slide with friction fallout
- StateDash: burst dash with momentum brake
- PlayerMovementController: entry point wiring to CharacterBody3D
- input_map.cfg: full action map reference file
- characters/player/player_base.tscn: placeholder scene
- movement/tests/test_fsm_runner.gd: 9-state unit test runner

Closes #1

movement/states/state_dash.gd

@@ -0,0 +1,45 @@
+extends Node
+class_name StateDash
+
+var machine: MovementStateMachine
+var params: MovementParams:
+	get: return machine.params
+
+var elapsed: float = 0.0
+var direction: Vector3 = Vector3.ZERO
+var dash_cooldown_timer: float = 0.0
+
+
+func enter(_data: Dictionary = {}) -> void:
+	elapsed = 0.0
+	dash_cooldown_timer = params.dash_cooldown
+	var input_v := machine.input_dir
+	var wish_dir := Vector3(input_v.x, 0.0, -input_v.y)
+	if wish_dir.length_squared() > 0.0:
+		direction = wish_dir.normalized()
+	else:
+		direction = -machine.player.global_transform.basis.z.normalized()
+		direction.y = 0.0
+		direction = direction.normalized()
+	direction = (machine.player.global_transform.basis * Vector4(direction.x, 0.0, direction.y, 0.0)).normalized()
+	machine.register_chain_mechanic("dash")
+	machine.player.velocity = direction * machine.get_effective_speed(params.dash_speed)
+	machine.on_ground = false
+
+
+func exit() -> void:
+	pass
+
+
+func update(delta: float) -> void:
+	elapsed += delta
+	dash_cooldown_timer -= delta
+	if elapsed > params.dash_duration:
+		machine.switch_to("air")
+		return
+	# Skip gravity, maintain dash velocity
+	machine.player.velocity = direction * machine.get_effective_speed(params.dash_speed)
+	machine.player.move_and_slide()
+	if machine.player.is_on_floor():
+		machine.on_ground = true
+		machine.switch_to("ground")