CI: add rust/ build+test workflow

data/dungeons/harkyn_3.json

@@ -0,0 +1,31 @@
+{
+  "id": "harkyn_3",
+  "name": "Harkyn's Castle - Level 3",
+  "dungeon": "harkyn",
+  "level": 3,
+  "width": 22,
+  "height": 22,
+  "description": "The deepest level of Harkyn's Castle. The Mad God is imprisoned here. The Old Man waits to guide those who prove worthy.",
+  "encounter_level": 5,
+  "special_squares": [
+    { "x": 0, "y": 0, "type": "stairs_up", "destination": "harkyn_2", "label": "Return to Harkyn's Level 2" },
+    { "x": 21, "y": 0, "type": "stairs_up", "destination": "skara_brae", "label": "Secret exit to Skara Brae" },
+    { "x": 11, "y": 11, "type": "special_encounter", "text": "The Mad God! A being of chaotic energy imprisoned by Harkyn long ago!", "encounter": "mad_god" },
+    { "x": 5, "y": 5, "type": "special_encounter", "text": "A mysterious Old Man sits by a magical fire. He offers guidance.", "encounter": "old_man" },
+    { "x": 10, "y": 3, "type": "anti_magic", "text": "The Mad God's prison radiates anti-magic energy. Spells are nullified." },
+    { "x": 15, "y": 7, "type": "trap", "text": "The Mad God's rage manifests! Psychic energy tears at your mind!", "damage": "3d6" },
+    { "x": 4, "y": 10, "type": "darkness", "text": "Only the Mad God's eerie glow illuminates this chamber." },
+    { "x": 17, "y": 14, "type": "silence", "text": "The Mad God's presence creates a bubble of unnatural silence." },
+    { "x": 8, "y": 16, "type": "spinner", "text": "Reality warps near the Mad God's prison. Directions become meaningless." },
+    { "x": 14, "y": 18, "type": "message", "text": "Inscriptions: 'The Mad God holds the key. Free him, and gain an ally against Mangar.'" },
+    { "x": 20, "y": 10, "type": "trap", "text": "Magical chains lash out from the walls!", "damage": "2d8" },
+    { "x": 3, "y": 17, "type": "special_encounter", "text": "A demon guardian summoned by Harkyn blocks your path!", "encounter": "harkyn_demon" },
+    { "x": 18, "y": 3, "type": "message", "text": "Harkyn's final journal: 'Mangar grows stronger. The Mad God is our last hope.'" },
+    { "x": 7, "y": 8, "type": "trap", "text": "The floor erupts with spectral energy!", "damage": "2d6" },
+    { "x": 19, "y": 19, "type": "message", "text": "A magical portal shimmers - it leads to Kylearan's Tower." }
+  ],
+  "connections": [
+    { "from_x": 0, "from_y": 0, "to": "harkyn_2", "type": "stairs_up" },
+    { "from_x": 21, "from_y": 0, "to": "skara_brae", "type": "stairs_up" }
+  ]
+}