Move items.jsonc under items/, add starter battle/moves.jsonc

Groups item data under assets/items/ to match the cutscenes/ folder
convention, updating itemInit()'s asset path accordingly. Also adds
assets/battle/moves.jsonc as a starting point for move data - there's
no JSON loader consuming it yet (battleability_t is still just a bare
enum), so its field shape is a placeholder rather than a contract.

Co-Authored-By: Claude Sonnet 5 <[email protected]>

assets/battle/moves.jsonc

@@ -0,0 +1,14 @@
+{
+  // Keyed by move id. "ability" matches a BATTLE_ABILITY_* enum name
+  // (see src/dusk/rpg/battle/battleability.h) - there's no JSON loader
+  // consuming this file yet, so field names/shape here are a starting
+  // point, not a contract.
+  "moves": {
+    "fire": {
+      "ability": "FIRE",
+      "power": 12,
+      "mpCost": 4,
+      "target": "SINGLE_ENEMY"
+    }
+  }
+}