docs: add proposal 13 — upgrade mainnet to v7.4.2

kiichain/proposals/proposal_13.json

@@ -0,0 +1,20 @@
+{
+    "messages": [
+        {
+            "@type": "/cosmos.upgrade.v1beta1.MsgSoftwareUpgrade",
+            "authority": "kii10d07y265gmmuvt4z0w9aw880jnsr700jrff0qv",
+            "plan": {
+                "name": "v7.4.2",
+                "time": "0001-01-01T00:00:00Z",
+                "height": "10250221",
+                "info": "",
+                "upgraded_client_state": null
+            }
+        }
+    ],
+    "metadata": "ipfs://CID",
+    "deposit": "20000000000000000000000akii",
+    "title": "Upgrade Kiichain to v7.4.2",
+    "summary": "Coordinated upgrade of Kiichain mainnet to v7.4.2.\n\nThe upgrade is scheduled for Monday 2026-09-21 around 17:00:00 UTC (block height 10,248,100).\n\nValidators should download the v7.4.2 binary, verify the checksum, and stage it in cosmovisor under the upgrade plan name v7.4.2 before the upgrade height.\n\nBinaries:\n- linux/amd64: https://kiichain-snapshots-public.s3.us-east-2.amazonaws.com/releases/v7.4.2/kiichaind-v7.4.2-linux-amd64\n  sha256: e99e145379c65b9a1b8dae1a799d9a359a16740c07d0c3684820e6729ab34513\n- linux/arm64: https://kiichain-snapshots-public.s3.us-east-2.amazonaws.com/releases/v7.4.2/kiichaind-v7.4.2-linux-arm64\n  sha256: 22df50464e13a69436213e54069eec26fe6468f2e88d0eb80e877bd883b63d49\n\nThis release updates CosmWasm dependencies and includes a no-op upgrade handler for plan name v7.4.2.",
+    "expedited": true
+}