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_wall_cling.gd

@@ -0,0 +1,52 @@
+extends Node
+class_name StateWallCling
+
+var machine: MovementStateMachine
+var params: MovementParams:
+	get: return machine.params
+
+var elapsed: float = 0.0
+
+
+func enter(_data: Dictionary = {}) -> void:
+	elapsed = 0.0
+	machine.register_chain_mechanic("wall_cling")
+
+
+func exit() -> void:
+	pass
+
+
+func update(delta: float) -> void:
+	elapsed += delta
+	var vel: Vector3 = machine.player.velocity
+	vel.x = params.wall_cling_horizontal_speed
+	vel.y = params.wall_cling_vertical_speed
+	vel.z = params.wall_cling_horizontal_speed
+	machine.player.velocity = vel
+	machine.player.move_and_slide()
+
+	# Jump off wall
+	if machine.input_jump_just_pressed:
+		var push_dir := machine.wall_normal * params.wall_run_jump_off_normal
+		var vel2 := Vector3(push_dir.x, params.jump_velocity, push_dir.z)
+		machine.player.velocity = vel2
+		machine.register_chain_mechanic("wall_cling_jump")
+		machine.switch_to("air")
+		return
+
+	# Re-enter wall run with input
+	if machine.input_dir.length() > 0.1:
+		machine.switch_to("wall_run")
+		return
+
+	# Fall
+	if not machine.wall_normal or machine.wall_normal.is_zero_approx():
+		machine.switch_to("air")
+		return
+
+	if machine.player.is_on_floor():
+		machine.on_ground = true
+		machine.wall_normal = Vector3.ZERO
+		machine.register_chain_mechanic("cling_land")
+		machine.switch_to("ground")