feat: 3D blobber dungeon generator (PR 1)

Replaces the 2D-only demo pipeline with a 3D cell-based blobber
generator. Per-cell face walls, per-material mesh emission, and a
GDExtension binding that returns a Dictionary with ArrayMesh surfaces
the demo consumes directly.

- src/blobber/: cell3d_t data model, dungeon container, pipeline that
  wraps the 2D generator per level and materializes into cell3d
- src/mesh/: face-quad emitter with per-material groups + .obj dump
- src/genesis3d_main.c: new CLI driving the blobber + mesh
- godot/: BrogueGen.generate_dungeon(seed, num_levels, depth) binding
  with dungeon_to_dict packing cells + mesh surfaces
- demo/: demo_blobber.tscn + dungeon_builder.gd, func_godot addon for
  the .map export path, point/entity templates, TrenchBroom docs
- Retired: old arcade/FPS demo scenes and their scripts, unused meshlib

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

demo/data/entities/func_lava/func_lava.tres

@@ -0,0 +1,14 @@
+[gd_resource type="Resource" script_class="FuncGodotFGDSolidClass" load_steps=2 format=3]
+
+[ext_resource type="Script" uid="uid://5cow84q03m6a" path="res://addons/func_godot/src/fgd/func_godot_fgd_solid_class.gd" id="1_script"]
+
+[resource]
+script = ExtResource("1_script")
+collision_shape_type = 2
+collision_mask = 0
+classname = "func_lava"
+description = "Lava volume. Party takes damage on entry and lasting burn debuff. Swap for a custom Area3D script to drive behavior."
+meta_properties = Dictionary[String, Variant]({
+"color": Color(0.95, 0.4, 0.1, 1)
+})
+node_class = "Area3D"

demo/data/entities/func_lava/func_lava.tscn

@@ -0,0 +1,3 @@
+[gd_scene format=3]
+
+[node name="func_lava" type="Area3D"]

demo/data/entities/func_water/func_water.tres

@@ -0,0 +1,14 @@
+[gd_resource type="Resource" script_class="FuncGodotFGDSolidClass" load_steps=2 format=3]
+
+[ext_resource type="Script" uid="uid://5cow84q03m6a" path="res://addons/func_godot/src/fgd/func_godot_fgd_solid_class.gd" id="1_script"]
+
+[resource]
+script = ExtResource("1_script")
+collision_shape_type = 2
+collision_mask = 0
+classname = "func_water"
+description = "Water volume. Party takes no damage but movement is slowed and fire is extinguished. Swap for a custom Area3D script to drive behavior."
+meta_properties = Dictionary[String, Variant]({
+"color": Color(0.15, 0.4, 0.75, 1)
+})
+node_class = "Area3D"

demo/data/entities/func_water/func_water.tscn

@@ -0,0 +1,3 @@
+[gd_scene format=3]
+
+[node name="func_water" type="Area3D"]

demo/data/entities/point_door/point_door.tres

@@ -0,0 +1,15 @@
+[gd_resource type="Resource" script_class="FuncGodotFGDPointClass" load_steps=3 format=3]
+
+[ext_resource type="Script" uid="uid://cxsqwtsqd8w33" path="res://addons/func_godot/src/fgd/func_godot_fgd_point_class.gd" id="1_script"]
+[ext_resource type="PackedScene" path="res://data/entities/point_door/point_door.tscn" id="2_scene"]
+
+[resource]
+script = ExtResource("1_script")
+scene_file = ExtResource("2_scene")
+apply_scale_on_map_build = false
+classname = "point_door"
+description = "Door marker placed on a door cell. 'angle' controls orientation. Behavior (open/close, locked) stubbed."
+meta_properties = Dictionary[String, Variant]({
+"color": Color(0.62, 0.38, 0.18, 1),
+"size": AABB(-8, -16, -8, 16, 48, 16)
+})

demo/data/entities/point_door/point_door.tscn

@@ -0,0 +1,3 @@
+[gd_scene format=3]
+
+[node name="point_door" type="Marker3D"]

demo/data/entities/point_player_start/point_player_start.tres

@@ -0,0 +1,15 @@
+[gd_resource type="Resource" script_class="FuncGodotFGDPointClass" load_steps=3 format=3]
+
+[ext_resource type="Script" uid="uid://cxsqwtsqd8w33" path="res://addons/func_godot/src/fgd/func_godot_fgd_point_class.gd" id="1_script"]
+[ext_resource type="PackedScene" path="res://data/entities/point_player_start/point_player_start.tscn" id="2_scene"]
+
+[resource]
+script = ExtResource("1_script")
+scene_file = ExtResource("2_scene")
+apply_scale_on_map_build = false
+classname = "point_player_start"
+description = "Dungeon party spawn at game start. Emitted once per exported .map at level 0's first stair-up (or first walkable cell if none)."
+meta_properties = Dictionary[String, Variant]({
+"color": Color(0.2, 0.6, 1, 1),
+"size": AABB(-16, -16, -16, 32, 32, 32)
+})

demo/data/entities/point_player_start/point_player_start.tscn

@@ -0,0 +1,3 @@
+[gd_scene format=3]
+
+[node name="point_player_start" type="Marker3D"]

demo/data/entities/point_stair_down/point_stair_down.tres

@@ -0,0 +1,15 @@
+[gd_resource type="Resource" script_class="FuncGodotFGDPointClass" load_steps=3 format=3]
+
+[ext_resource type="Script" uid="uid://cxsqwtsqd8w33" path="res://addons/func_godot/src/fgd/func_godot_fgd_point_class.gd" id="1_script"]
+[ext_resource type="PackedScene" path="res://data/entities/point_stair_down/point_stair_down.tscn" id="2_scene"]
+
+[resource]
+script = ExtResource("1_script")
+scene_file = ExtResource("2_scene")
+apply_scale_on_map_build = false
+classname = "point_stair_down"
+description = "Interact marker placed on a cell that should descend to the next level. Behavior (pickup, transition) stubbed."
+meta_properties = Dictionary[String, Variant]({
+"color": Color(0.85, 0.25, 0.2, 1),
+"size": AABB(-16, -16, -16, 32, 32, 32)
+})

demo/data/entities/point_stair_down/point_stair_down.tscn

@@ -0,0 +1,3 @@
+[gd_scene format=3]
+
+[node name="point_stair_down" type="Marker3D"]

demo/data/entities/point_stair_up/point_stair_up.tres

@@ -0,0 +1,15 @@
+[gd_resource type="Resource" script_class="FuncGodotFGDPointClass" load_steps=3 format=3]
+
+[ext_resource type="Script" uid="uid://cxsqwtsqd8w33" path="res://addons/func_godot/src/fgd/func_godot_fgd_point_class.gd" id="1_script"]
+[ext_resource type="PackedScene" path="res://data/entities/point_stair_up/point_stair_up.tscn" id="2_scene"]
+
+[resource]
+script = ExtResource("1_script")
+scene_file = ExtResource("2_scene")
+apply_scale_on_map_build = false
+classname = "point_stair_up"
+description = "Interact marker placed on a cell that should climb to the previous level. Behavior (pickup, transition) stubbed."
+meta_properties = Dictionary[String, Variant]({
+"color": Color(0.2, 0.8, 0.3, 1),
+"size": AABB(-16, -16, -16, 32, 32, 32)
+})

demo/data/entities/point_stair_up/point_stair_up.tscn

@@ -0,0 +1,3 @@
+[gd_scene format=3]
+
+[node name="point_stair_up" type="Marker3D"]