feat(anthrax-cat): add craftable item, recipe, and inventory entry

- Custom item silverlabs:anthrax_cat with entity_placer — place cat by right-clicking ground
- Shaped recipe: 4 gold ingots + 1 red dye (cross pattern) at crafting table
- Recipe unlocks when player has a gold ingot
- Item appears in creative inventory under Items > Misc
- Item icon: 16x16 Maneki-neko pixel art
- Set is_spawnable: false on entity (use crafted item instead of spawn egg)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

addon/anthrax_cat_BP/recipes/anthrax_cat.json

@@ -0,0 +1,25 @@
+{
+  "format_version": "1.21.0",
+  "minecraft:recipe_shaped": {
+    "description": {
+      "identifier": "silverlabs:anthrax_cat_recipe"
+    },
+    "tags": ["crafting_table"],
+    "unlock": [
+      { "item": "minecraft:gold_ingot" }
+    ],
+    "pattern": [
+      " G ",
+      "GRG",
+      " G "
+    ],
+    "key": {
+      "G": { "item": "minecraft:gold_ingot" },
+      "R": { "item": "minecraft:red_dye" }
+    },
+    "result": {
+      "item": "silverlabs:anthrax_cat",
+      "count": 1
+    }
+  }
+}