arb/robinhood: add nitro pruned-pebble-path compose for mainnet and testnet

Orbit rollup on Ethereum/Sepolia with per-chain baseConfig assets (testnet
info-json from official config; mainnet genesis-json-file bootstrap).

Co-authored-by: Cursor <cursoragent@cursor.com>

compose_registry.json

@@ -828,6 +828,40 @@
       "real-mainnet-nitro-pruned-pebble-path"
     ]
   },
+  {
+    "chain": "mainnet",
+    "client": "nitro",
+    "compose_file": "arb/nitro/robinhood-mainnet-nitro-pruned-pebble-path",
+    "features": [
+      "path",
+      "pebble"
+    ],
+    "network": "robinhood",
+    "node": null,
+    "relay": null,
+    "stack": "arb",
+    "type": "pruned",
+    "volumes": [
+      "robinhood-mainnet-nitro-pruned-pebble-path"
+    ]
+  },
+  {
+    "chain": "testnet",
+    "client": "nitro",
+    "compose_file": "arb/nitro/robinhood-testnet-nitro-pruned-pebble-path",
+    "features": [
+      "path",
+      "pebble"
+    ],
+    "network": "robinhood",
+    "node": null,
+    "relay": null,
+    "stack": "arb",
+    "type": "pruned",
+    "volumes": [
+      "robinhood-testnet-nitro-pruned-pebble-path"
+    ]
+  },
   {
     "chain": "sepolia",
     "client": "nitro-erigon",