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.

system/drivers/pci-bus/pci-bus.zig

@@ -21,7 +21,7 @@ const logging = @import("logging");
 const device_manager_protocol = @import("device-manager-protocol");
 const pci_class = @import("pci-class");
 
-/// Log a discovered function as its would-be /etc/devices.csv columns (bus, base,
+/// Log a discovered function as its would-be /system/configuration/devices.csv columns (bus, base,
 /// class, prog_if, vendor, device, subsystem) followed by the human-readable
 /// class/subclass/prog-IF names — so a row for a new driver reads straight off the
 /// boot log. `subsystem` prints as `*` when the function has none, matching the CSV
@@ -154,7 +154,7 @@ fn registerAndReport(bus: u64, dev: u64, function: u64, class_triple: u32) void
     descriptor.class = @intFromEnum(device.DeviceClass.pci_device);
     descriptor.pci_class = class_triple;
     // Vendor/device from the first config dword (0x00): low half vendor, high half
-    // device. These carry to the manager's /etc/devices.csv matcher so a function
+    // device. These carry to the manager's /system/configuration/devices.csv matcher so a function
     // can bind on its exact 1AF4:1050 identity, not just its class triple.
     const vendor_device = configRead(bus, dev, function, 0x00);
     descriptor.vendor = @truncate(vendor_device);

system/drivers/usb-xhci-bus/usb-xhci-bus.zig

@@ -459,7 +459,7 @@ fn reportInterface(manager: ipc.Handle, port: u32, interface: library.InterfaceI
         return null;
     };
     // The devices.csv columns (bus=usb, and the class triple as base/class/prog_if)
-    // then the human-readable interface name — a would-be /etc/devices.csv row read
+    // then the human-readable interface name — a would-be /system/configuration/devices.csv row read
     // straight off the boot log.
     std.log.info("port {d} interface {d}  bus=usb base={X:0>2} class={X:0>2} prog_if={X:0>2}  —  {s}  registered as device {d}", .{
         port,

system/drivers/virtio-gpu/virtio-gpu.zig

@@ -205,7 +205,7 @@ fn initialise(endpoint: ipc.Handle) bool {
         return false;
     };
 
-    // Config space is resource 0. The registry (/etc/devices.csv) bound this driver by the
+    // Config space is resource 0. The registry (/system/configuration/devices.csv) bound this driver by the
     // exact virtio-gpu identity (vendor 0x1AF4 / device 0x1050), so there is no re-confirm to
     // do here any more — map config space and enable memory-space decode + bus mastering (the
     // device DMAs the ring and backing out of RAM; pci-bus only preserves whatever the firmware