feat(assets): 3D sprite render pipeline — camera, lighting, docs (#541)

Update Camera3D to exact D-019 angle (-72.5° from horizontal).
Replace single DirectionalLight with three-point studio rig
(key 1.0, fill 0.4, rim 0.3) for clean silhouettes without
baked shadows. Add generic NPC capsule model (24×32px footprint
per D-044). Document full pipeline spec in renderer/README.md.

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

renderer/models/npc_generic.tscn

@@ -0,0 +1,14 @@
+[gd_scene load_steps=3 format=3 uid="uid://npcgeneric001"]
+
+[sub_resource type="CapsuleMesh" id="CapsuleMesh_npc"]
+radius = 0.25
+height = 0.62
+
+[sub_resource type="StandardMaterial3D" id="StandardMaterial3D_npc"]
+albedo_color = Color(0.5, 0.5, 0.5, 1.0)
+metallic = 0.0
+roughness = 0.9
+
+[node name="NpcGeneric" type="MeshInstance3D"]
+mesh = SubResource("CapsuleMesh_npc")
+surface_material_override/0 = SubResource("StandardMaterial3D_npc")