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_air.gd

@@ -0,0 +1,70 @@
+extends Node
+class_name StateAir
+
+var machine: MovementStateMachine
+var params: MovementParams:
+	get: return machine.params
+
+
+func enter(_data: Dictionary = {}) -> void:
+	pass
+
+
+func exit() -> void:
+	pass
+
+
+func update(delta: float) -> void:
+	var vel: Vector3 = machine.player.velocity
+
+	# Apply standard gravity
+	vel.y -= params.gravity * delta
+
+	# Input direction
+	var input_v := machine.input_dir
+	var wish_dir := Vector3(input_v.x, 0.0, -input_v.y)
+	if wish_dir.length_squared() > 1.0:
+		wish_dir = wish_dir.normalized()
+
+	var effective_speed := machine.get_effective_speed(params.max_air_speed)
+
+	var hvel := Vector3(vel.x, 0.0, vel.z)
+	var target_vel := wish_dir * effective_speed * params.air_control
+
+	hvel = hvel.lerp(Vector3(hvel.x + target_vel.x, 0.0, hvel.z + target_vel.z), 1.0 - exp(-params.air_acceleration * delta))
+
+	vel.x = hvel.x
+	vel.z = hvel.z
+
+	# Bunny hop: if jump pressed and on ground near-peak of arc → extra boost
+	if machine.input_jump_just_pressed and machine.on_ground:
+		vel.y = params.jump_velocity * params.bunny_hop_impulse
+		machine.player.velocity = vel
+		machine.register_chain_mechanic("bunny_hop")
+		machine.current_jump_count += 1
+		machine.on_ground = false
+		machine.switch_to("air")
+		return
+
+	# Double Jump
+	if machine.input_jump_just_pressed and not machine.on_ground and machine.current_jump_count < params.double_jump_max_count:
+		vel.y = params.double_jump_velocity
+		machine.player.velocity = vel
+		machine.current_jump_count += 1
+		machine.register_chain_mechanic("double_jump")
+		machine.switch_to("air")
+		return
+
+	machine.player.velocity = vel
+	machine.player.move_and_slide()
+
+	# Landing
+	if machine.player.is_on_floor():
+		machine.on_ground = true
+		machine.current_jump_count = 0
+		machine.switch_to("ground")
+		return
+
+	# Wall run transition
+	if not machine.wall_normal.is_zero_approx():
+		machine.switch_to("wall_run")