fraxtal-mainnet: add fjord/granite/holocene/isthmus fork times to genesis.json (check_fork_times --fix)

Source: FraxFinance/fraxtal-node master mainnet/rollup.json (published; RPCs refuse
optimism_rollupConfig). rollup.json already had them; genesis.json stopped at
ecotone so op-geth (geth init runs every start) never activated Fjord+.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RzxemENdcZBCxdGrzXiFvS

op/fraxtal/mainnet/genesis.json

@@ -27,7 +27,11 @@
       "eip1559Elasticity": 10,
       "eip1559Denominator": 50,
       "eip1559DenominatorCanyon": 250
-    }
+    },
+    "fjordTime": 1733947201,
+    "graniteTime": 1738958401,
+    "holoceneTime": 1744052401,
+    "isthmusTime": 1755716401
   },
   "nonce": "0x0",
   "timestamp": "0x65bbdd57",