Initial commit: Theriapolis baseline at port/godot branch point

Captures the pre-Godot-port state of the codebase. This is the rollback
anchor for the Godot port (M0 of theriapolis-rpg-implementation-plan-godot-port.md).
All Phase 0 through Phase 6.5 work is included; Phase 7 is in flight.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Content/Data/room_templates/mine/mineral_vein_room.json

@@ -0,0 +1,28 @@
+{
+  "id": "mine.mineral_vein_room",
+  "name": "Mineral Vein Chamber",
+  "type": "mine",
+  "built_by": "none",
+  "size_class": "medium",
+  "roles_eligible": ["transit", "loot", "dead-end"],
+  "footprint_w_tiles": 10,
+  "footprint_h_tiles": 8,
+  "grid": [
+    "##########",
+    "#........#",
+    "#........#",
+    "D...C....#",
+    "#........#",
+    "#........#",
+    "#........#",
+    "##########"
+  ],
+  "doors": [
+    { "x": 0, "y": 3, "facing": "W" }
+  ],
+  "container_slots": [
+    { "x": 4, "y": 3, "loot_table_band": "t1" }
+  ],
+  "narrative_text": "A dark seam in the rock catches the lantern-light: copper, maybe silver beneath. The miners who broke this open never came back to finish the job.",
+  "weight": 1.0
+}