Operators can now define Hunting Road configuration in a plain JSON file
(rengoku_data.json) instead of maintaining an opaque pre-encrypted binary.
The JSON is parsed, validated, assembled into the binary layout, and
ECD-encrypted at startup; rengoku_data.bin is still used as a fallback.
JSON schema covers both road modes (multi/solo) with typed floor and
spawn-table entries — floor number, spawn-table index, point multipliers,
and per-slot monster ID/variant/weighting fields. Out-of-range references
are caught at load time before any bytes are written.