Initial commit — Station 0 vertical slice in progress

Includes full design documentation (ARCHITECTURE, DESIGN_NOTES, CONTENT_SPEC, PRODUCTION_NOTES)
and active Godot 4 / GDScript codebase. Core systems built: player, floor generation,
room system, enemy base, body part upgrades, run manager, save system, HUD, EventBus.

data/body_parts/right_arm_cannon.tres

@@ -0,0 +1,9 @@
+[gd_resource type="Resource" script_class="BodyPartData" load_steps=2 format=3]
+
+[ext_resource type="Script" path="res://scripts/upgrades/body_part_data.gd" id="1"]
+
+[resource]
+script = ExtResource("1")
+slot = "right_arm"
+display_name = "Cannon Arm"
+mod_damage = 1.5