CI: add rust/ build+test workflow

data/dungeons/sewers_3.json

@@ -0,0 +1,34 @@
+{
+  "id": "sewers_3",
+  "name": "Sewers - Level 3",
+  "dungeon": "sewers",
+  "level": 3,
+  "width": 22,
+  "height": 22,
+  "description": "The deepest sewers. The goblin chieftain rules from here, and passages branch to the Catacombs and Harkyn's Castle.",
+  "encounter_level": 3,
+  "special_squares": [
+    { "x": 0, "y": 0, "type": "stairs_up", "destination": "sewers_2", "label": "Return to Sewers Level 2" },
+    { "x": 21, "y": 0, "type": "stairs_down", "destination": "catacombs_1", "label": "Descend to Catacombs" },
+    { "x": 0, "y": 21, "type": "stairs_down", "destination": "harkyn_1", "label": "Secret passage to Harkyn's Castle" },
+    { "x": 11, "y": 11, "type": "special_encounter", "text": "The Goblin Chieftain rises from his throne of bones!", "encounter": "goblin_chieftain" },
+    { "x": 7, "y": 5, "type": "darkness", "text": "The only light comes from glowing fungal patches on the ceiling." },
+    { "x": 16, "y": 3, "type": "anti_magic", "text": "Dark energy radiates from a cracked altar. Magic is suppressed." },
+    { "x": 4, "y": 9, "type": "trap", "text": "A spiked pit opens beneath you!", "damage": "2d8" },
+    { "x": 14, "y": 8, "type": "spinner", "text": "The passages here form a confusing maze of identical corridors." },
+    { "x": 9, "y": 15, "type": "silence", "text": "Even the water runs silent here. An eerie, oppressive quiet." },
+    { "x": 19, "y": 14, "type": "trap", "text": "Poison darts shoot from the walls!", "damage": "2d4" },
+    { "x": 6, "y": 17, "type": "message", "text": "The goblin chieftain's treasure hoard - mostly worthless trinkets and a few gems." },
+    { "x": 12, "y": 18, "type": "special_encounter", "text": "Wraiths materialize from the shadows!", "encounter": "sewer_wraiths" },
+    { "x": 2, "y": 3, "type": "message", "text": "The walls here are older than the rest - smooth stone from the original construction." },
+    { "x": 17, "y": 6, "type": "darkness", "text": "A section of tunnel has collapsed. You must squeeze through the rubble." },
+    { "x": 20, "y": 19, "type": "message", "text": "A crude sign reads 'HARKYN'S PASSAGE' with an arrow pointing left." },
+    { "x": 15, "y": 20, "type": "trap", "text": "Swarm of sewer rats bites at your ankles!", "damage": "1d6" },
+    { "x": 8, "y": 11, "type": "spinner", "text": "Three-way intersection with identical corridors. You choose at random." }
+  ],
+  "connections": [
+    { "from_x": 21, "from_y": 0, "to": "catacombs_1", "type": "stairs_down" },
+    { "from_x": 0, "from_y": 21, "to": "harkyn_1", "type": "stairs_down" },
+    { "from_x": 0, "from_y": 0, "to": "sewers_2", "type": "stairs_up" }
+  ]
+}