Add scene-authored FX library and bull ability effects

An Fx autoload + one_shot_effect base so every effect is an inspector-editable
.tscn (the systems/fx/ authoring dir): blood/slam/spark/flash primitives and the
bull's kick/dash/slam/roll + movement effects (bull_*.tscn), fired via
Fx.spawn() / Fx.attach(). Plus a preview gallery + smoke test, and
bull_impact_fx.gd for the coded, non-particle slam rings + kick flash-pop.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CCyaJPTHCH9EDthpf4A5Sj

actors/player/bull_impact_fx.gd

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+extends Node
+## Procedural (non-particle) bull impact FX: the expanding ground-slam shockwave rings and the
+## kick flash-pop. These are tween-animated MeshInstance3D flashes, not CPUParticles3D, so they
+## can't be authored as systems/fx/ scenes and live in code here. Created by player.gd; the
+## transient meshes are parented into the level (the bull's parent) so they hold their world
+## position while the bull keeps moving.
+
+var _player: Node3D
+var _ring_mesh: ArrayMesh = null
+
+
+func setup(player: Node3D) -> void:
+	_player = player
+
+
+# Three nested shockwave rings racing outward from a ground slam, each fading as it grows.
+func slam_rings(origin: Vector3, max_r: float) -> void:
+	if _ring_mesh == null:
+		_ring_mesh = _make_ring_mesh()
+	_launch_ring(origin, max_r, 0.00, 0.55, Color(1.0, 0.70, 0.10, 0.85))
+	_launch_ring(origin, max_r, 0.10, 0.52, Color(1.0, 0.50, 0.10, 0.65))
+	_launch_ring(origin, max_r, 0.20, 0.48, Color(0.9, 0.30, 0.10, 0.50))
+
+
+# A quick bright flash-pop at the kick's contact point.
+func kick_flash(origin: Vector3) -> void:
+	var mat := _flat_material(Color(1.0, 0.97, 0.40, 0.0))
+	var sphere := SphereMesh.new()
+	sphere.radius = 1.0
+	sphere.height = 2.0
+	sphere.radial_segments = 8
+	sphere.rings = 4
+	sphere.material = mat
+
+	var mi := MeshInstance3D.new()
+	mi.mesh = sphere
+	mi.material_override = mat
+	mi.scale = Vector3(0.05, 0.05, 0.05)
+	_host().add_child(mi)
+	mi.global_position = origin
+
+	var tween := create_tween()
+	tween.set_parallel(true)
+	tween.tween_property(mi, "scale", Vector3(0.7, 0.7, 0.7), 0.13)\
+		.set_trans(Tween.TRANS_EXPO).set_ease(Tween.EASE_OUT)
+	var fade := func(a: float) -> void: mat.albedo_color.a = a
+	tween.tween_method(fade, 0.92, 0.0, 0.14)\
+		.set_trans(Tween.TRANS_SINE).set_ease(Tween.EASE_IN)
+	tween.tween_callback(mi.queue_free).set_delay(0.16)
+
+
+func _launch_ring(origin: Vector3, max_r: float, delay: float, duration: float, col: Color) -> void:
+	var mat := _flat_material(Color(col.r, col.g, col.b, 0.0))
+	var mi := MeshInstance3D.new()
+	mi.mesh = _ring_mesh
+	mi.material_override = mat
+	mi.scale = Vector3(0.02, 1.0, 0.02)
+	_host().add_child(mi)
+	mi.global_position = origin
+
+	var tween := create_tween()
+	tween.set_parallel(true)
+	tween.tween_property(mi, "scale", Vector3(max_r, 1.0, max_r), duration)\
+		.set_delay(delay).set_trans(Tween.TRANS_EXPO).set_ease(Tween.EASE_OUT)
+	var fade := func(a: float) -> void: mat.albedo_color.a = a
+	tween.tween_method(fade, col.a, 0.0, duration)\
+		.set_delay(delay).set_trans(Tween.TRANS_SINE).set_ease(Tween.EASE_IN)
+	tween.tween_callback(mi.queue_free).set_delay(delay + duration + 0.05)
+
+
+func _flat_material(color: Color) -> StandardMaterial3D:
+	var mat := StandardMaterial3D.new()
+	mat.shading_mode = BaseMaterial3D.SHADING_MODE_UNSHADED
+	mat.transparency = BaseMaterial3D.TRANSPARENCY_ALPHA
+	mat.cull_mode = BaseMaterial3D.CULL_DISABLED
+	mat.albedo_color = color
+	return mat
+
+
+# A flat annulus in the XZ plane (unit radius), scaled up at runtime into the shockwave ring.
+func _make_ring_mesh() -> ArrayMesh:
+	const INNER_R: float = 0.82
+	const OUTER_R: float = 1.00
+	const SEGMENTS: int = 48
+
+	var verts := PackedVector3Array()
+	var indices := PackedInt32Array()
+	for i: int in SEGMENTS:
+		var a0 := i / float(SEGMENTS) * TAU
+		var a1 := (i + 1) / float(SEGMENTS) * TAU
+		var vi := i * 4
+		verts.append(Vector3(cos(a0) * INNER_R, 0.0, sin(a0) * INNER_R))
+		verts.append(Vector3(cos(a0) * OUTER_R, 0.0, sin(a0) * OUTER_R))
+		verts.append(Vector3(cos(a1) * OUTER_R, 0.0, sin(a1) * OUTER_R))
+		verts.append(Vector3(cos(a1) * INNER_R, 0.0, sin(a1) * INNER_R))
+		indices.append_array([vi, vi + 2, vi + 1, vi, vi + 3, vi + 2])
+
+	var arrays: Array = []
+	arrays.resize(Mesh.ARRAY_MAX)
+	arrays[Mesh.ARRAY_VERTEX] = verts
+	arrays[Mesh.ARRAY_INDEX] = indices
+	var mesh := ArrayMesh.new()
+	mesh.add_surface_from_arrays(Mesh.PRIMITIVE_TRIANGLES, arrays)
+	return mesh
+
+
+func _host() -> Node:
+	if _player != null and _player.get_parent() != null:
+		return _player.get_parent()
+	return _player

actors/player/bull_impact_fx.gd.uid

@@ -0,0 +1 @@
+uid://sf5etma4kjt0