feat(biome): abyssal bioluminescent + glow blocks + abyssal jellyfish + particles

- BlockDatabase: GLOW_CORAL_CYAN(10), GLOW_CORAL_VIOLET(11), LAVA_VENT(12) with emission data
- WorldGenerator: abyssal blocks at y<-40 (cyan 4%, violet 1%, vent 0.5% via 3D noise)
- Chunk.gd: multi-surface mesh (solid + 3 emissive surfaces with StandardMaterial3D emission)
- MobSpawner: abyssal jellyfish spawn when player y<-30, max 8
- AbyssalJellyfish: cyan fluo, slower, double damage (10), bioluminescent flash on attack
- BioluminescentParticles: 200 cyan-green particles follow player, only emit in abyss

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

scenes/mobs/AbyssalJellyfish.tscn

@@ -0,0 +1,11 @@
+[gd_scene load_steps=2 format=3 uid="uid://abyssaljellyfish001"]
+
+[ext_resource type="Script" path="res://scripts/mobs/AbyssalJellyfish.gd" id="1_abyssaljelly"]
+
+[node name="AbyssalJellyfish" type="CharacterBody3D"]
+script = ExtResource("1_abyssaljelly")
+max_health = 25.0
+damage = 10.0
+detection_radius = 8.0
+attack_radius = 1.5
+move_speed = 0.6