Move bull ability FX into the authorable systems/fx/ library

The bull's kick/dash/slam/roll and movement particles were ~112 lines of
hand-built CPUParticles3D in player.gd, bypassing the Fx system entirely
(Fx.spawn had zero callers) — so Siim couldn't author them in the inspector.

- Add six inspector-editable effect scenes (bull_slam/kick/dash one-shots +
  bull_hoof_dust/charge_trail/roll_sparks continuous); wire player.gd to
  Fx.spawn() / new Fx.attach(); register them + the gallery + smoke test.
- Extract the coded, non-particle slam rings + kick flash into a new
  bull_impact_fx.gd component (bull_legs.gd pattern).
- Drop 12 now-obsolete DP dust look-params (the .tscn owns the look now).
- Trim god-file comment noise: rewrite an AI-placeholder barrel block to typed
  code, drop dead commented-out bounce/topple code, fix stale post-reorg file
  paths (Assets/… → art/…, PascalCase scene names → snake_case).
- Document the Siim workflow in systems/fx/README.md; update CLAUDE.md.

player.gd 1307 → 944 lines. Full suite green.

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

systems/fx/fx.gd

@@ -7,10 +7,18 @@ extends Node
 ## placeholder .tscn are seeded — see tools/seed_fx_placeholders.gd.
 
 const _PATHS: Dictionary = {
+	# Generic hit effects.
 	&"blood_burst": "res://systems/fx/blood_burst.tscn",
 	&"slam_dust": "res://systems/fx/slam_dust.tscn",
 	&"spark": "res://systems/fx/spark.tscn",
 	&"hit_flash": "res://systems/fx/hit_flash.tscn",
+	# Bull ability effects — one-shots fired by spawn(), continuous ones held via attach().
+	&"bull_slam": "res://systems/fx/bull_slam.tscn",
+	&"bull_kick": "res://systems/fx/bull_kick.tscn",
+	&"bull_dash": "res://systems/fx/bull_dash.tscn",
+	&"bull_hoof_dust": "res://systems/fx/bull_hoof_dust.tscn",
+	&"bull_charge_trail": "res://systems/fx/bull_charge_trail.tscn",
+	&"bull_roll_sparks": "res://systems/fx/bull_roll_sparks.tscn",
 }
 
 var _cache: Dictionary = {}
@@ -32,6 +40,18 @@ func spawn(effect: StringName, xform: Transform3D, parent: Node = null) -> Node:
 	return inst
 
 
+# Instance a CONTINUOUS effect as a child of `parent` and hand it back. Unlike spawn(), it neither
+# positions nor auto-frees the effect — the caller keeps the reference to place it and toggle
+# `emitting` (hoof dust that follows the bull, the charge trail). Returns null if unknown/missing.
+func attach(effect: StringName, parent: Node) -> Node:
+	var scene := _scene(effect)
+	if scene == null or parent == null:
+		return null
+	var inst := scene.instantiate()
+	parent.add_child(inst)
+	return inst
+
+
 func _scene(effect: StringName) -> PackedScene:
 	if _cache.has(effect):
 		return _cache[effect]