napple-build: sysdata::write_system_archives writes firmware data archives 0100000000000800-0FFF (RomFS image, ≤64 MiB) to <title dir>/sysdata/<id>.bin; called from the pipeline when --firmware is given; compat note if 0823 is missing. napple-core RomFs::image() added. [verified on Firmware 22.1.0: 40 files]
fs.c: OpenDataStorageByDataId also looks in <data-dir>/../sysdata/. [tested: test_svc_fs; verified on AC v0]
Not done: ids beyond 0x800-0xFFF range or >64 MiB; app-bundle layout not run (only --data-only built).