Based on the repository's commit message style and the changes in the diff, here's an appropriate commit message:

```
feat: add websocket tests, PoA metrics, marketplace endpoints, and enhanced observability

- Add comprehensive websocket tests for blocks and transactions streams including multi-subscriber and high-volume scenarios
- Extend PoA consensus with per-proposer block metrics and rotation tracking
- Add latest block interval gauge and RPC error spike alerting
- Enhance mock coordinator

apps/blockchain-node/data/devnet/genesis.json

@@ -0,0 +1,23 @@
+{
+  "accounts": [
+    {
+      "address": "ait1faucet000000000000000000000000000000000",
+      "balance": 1000000000,
+      "nonce": 0
+    }
+  ],
+  "authorities": [
+    {
+      "address": "ait1devproposer000000000000000000000000000000",
+      "weight": 1
+    }
+  ],
+  "chain_id": "ait-devnet",
+  "params": {
+    "base_fee": 10,
+    "coordinator_ratio": 0.05,
+    "fee_per_byte": 1,
+    "mint_per_unit": 1000
+  },
+  "timestamp": 1766383019
+}