partition.zig gains an exFAT VBR recognizer: the "EXFAT " name (where a
FAT BPB keeps its OEM string, so the two never collide) plus the 0x55AA
signature, with VolumeSerialNumber (offset 100) as a new exfat_serial
identity rung. A `recognize` helper tries exFAT, then FAT, then the MBR
disk-signature fallback, and sets each volume's FilesystemKind — so
allVolumes/firstVolume and the GPT path all tag a volume with the engine
its content needs. volume-map renders exfat-<serial> as the id-path, and
filesystems.csv adds the exfat -> /system/services/exfat row: an exFAT
stick now spawns the exFAT service, at its own content id-path.
Host tests: a bare exFAT volume recognized with its serial; a FAT VBR
still recognized as fat (the discrimination); the exfat-<serial> id
render. build + zig build test + bounds green.
The volume manager reads its policy from configuration at boot (loadTables,
mirroring the device-manager registry load): filesystems.csv (content signature
-> service binary) and volumes.csv (optional id -> mount-prefix override), each
held in a static source buffer with declared bounds. On probe it picks the
binary from the volume's signature (unserved + logged if no row matches, like an
unbound device) and composes the mount path — a volumes.csv override, else the
default /volumes/<id> from volume-map.idString — then spawns that binary with
argv {volume-id, mount-prefix}. Behavior-preserving: fat still ignores argv[2..]
and uses its hardcoded mounts, the binary resolves to /system/services/fat, so
the FULL suite stays green (127/127); the flip to argv-driven mounts and the
/volumes/usb -> id-path migration land in step 5.
Daniel Samson