build: the unix paths retire — configuration, logs, and volumes move into the danos tree

/etc/init.csv and /etc/devices.csv become /system/configuration/*.csv (the
repo's etc/ moves to system/configuration/, mirroring the runtime tree),
/var/log becomes /system/logs, and /mnt/usb becomes /volumes/usb. The
kernel VFS gains a carve-out so FAT may serve exactly /system/configuration
and /system/logs beneath the initrd-backed /system while /system and /test
themselves stay unshadowable; FAT's single /var mount splits into those two
rewritten mounts. The kvfs readdir check learns /system's third child and
the ramdisk spawn sweep skips the configuration tree.

Suite 106/106.

library/csv/build.zig

@@ -1,5 +1,5 @@
 //! The "csv" library domain: shared CSV helpers (comment stripping, field
-//! iteration) for the /etc/*.csv config files — the device registry and the
+//! iteration) for the /system/configuration/*.csv config files — the device registry and the
 //! init service list both parse them.
 
 const std = @import("std");