arc: add mainnet (chain 5042) — reth EL + malachite CL

Mirror arc-testnet for mainnet: --chain=arc-mainnet (bundled genesis, chainspec.rs
ARC_SUPPORTED), drpc chain 'arc' (CHAIN_ARC__MAINNET), forwarder rpc.arc.network.
malachite follows rpc.arc.network + arc.drpc.org (testnet endpoints are testnet-only
in Circle's docs). Generates arc/reth/arc-mainnet-reth-{pruned,archive}-trace.yml.

compose_registry.json

@@ -876,6 +876,42 @@
       "arbitrum-sepolia-nitro-erigon-pruned-trace"
     ]
   },
+  {
+    "chain": "mainnet",
+    "client": "reth",
+    "compose_file": "arc/reth/arc-mainnet-reth-archive-trace",
+    "features": [
+      "trace"
+    ],
+    "network": "arc",
+    "node": "malachite",
+    "relay": null,
+    "stack": null,
+    "type": "archive",
+    "volumes": [
+      "arc-mainnet-reth-archive-trace-consensus",
+      "arc-mainnet-reth-archive-trace-execution",
+      "arc-mainnet-reth-archive-trace-sockets"
+    ]
+  },
+  {
+    "chain": "mainnet",
+    "client": "reth",
+    "compose_file": "arc/reth/arc-mainnet-reth-pruned-trace",
+    "features": [
+      "trace"
+    ],
+    "network": "arc",
+    "node": "malachite",
+    "relay": null,
+    "stack": null,
+    "type": "pruned",
+    "volumes": [
+      "arc-mainnet-reth-pruned-trace-consensus",
+      "arc-mainnet-reth-pruned-trace-execution",
+      "arc-mainnet-reth-pruned-trace-sockets"
+    ]
+  },
   {
     "chain": "testnet",
     "client": "reth",