feat(dolphin): swim controller + third-person camera + HUD stats

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

scripts/dolphin/EcholocationPulse.gd

@@ -0,0 +1,46 @@
+extends Node3D
+
+const MAX_RADIUS: float = 20.0
+const DURATION: float = 1.0
+
+signal pulse_finished()
+
+
+func trigger() -> void:
+	var mesh_instance := MeshInstance3D.new()
+	var sphere_mesh := SphereMesh.new()
+	sphere_mesh.radius = 0.1
+	sphere_mesh.height = 0.2
+	mesh_instance.mesh = sphere_mesh
+
+	var mat := StandardMaterial3D.new()
+	mat.transparency = BaseMaterial3D.TRANSPARENCY_ALPHA
+	mat.albedo_color = Color(0.2, 0.85, 1.0, 0.5)
+	mat.emission_enabled = true
+	mat.emission = Color(0.1, 0.6, 1.0)
+	mat.emission_energy_multiplier = 1.5
+	mat.cull_mode = BaseMaterial3D.CULL_DISABLED
+	mesh_instance.material_override = mat
+
+	add_child(mesh_instance)
+
+	var tween: Tween = create_tween()
+	tween.set_parallel(true)
+	tween.tween_method(
+		func(r: float) -> void:
+			mesh_instance.scale = Vector3(r, r, r),
+		0.1,
+		MAX_RADIUS,
+		DURATION
+	)
+	tween.tween_method(
+		func(a: float) -> void:
+			mat.albedo_color = Color(0.2, 0.85, 1.0, a),
+		0.5,
+		0.0,
+		DURATION
+	)
+	tween.chain().tween_callback(func() -> void:
+		mesh_instance.queue_free()
+		pulse_finished.emit()
+	)