boot: the /system tree is the system image — loader-built ramdisk, spawn by path

Retire the build-time ramdisk packer and the packed initial-ramdisk.img.
make-fat-image.py now lays every user binary out at its FHS path on the
boot volume (system/services, system/drivers, system/tests), and the EFI
loader walks \system at boot, packing what it finds into an in-RAM v2
initial_ramdisk whose entry names are full FHS paths. init rides the
table like every other binary: its dedicated handoff fields are gone and
the kernel spawns PID 1 via the same lookup as everyone else
(process.spawnBundled).

system_spawn resolves names by exact path first, then unique basename,
and normalizes argv[0] to the stored path — so task names (and, next,
the tagged log ring's attribution) are honest binary paths everywhere.
initrd v2 rejects the old magic so a stale image fails loudly.

Groundwork for per-process logging (/var/log/<boot-stamp>/<binary-path>.log)
and the kernel-VFS /system mount.

system/services/device-manager/device-manager.zig

@@ -56,8 +56,8 @@ const virtio_gpu_pci_class: u64 = pci_class.ClassCode.pack(.{
 /// its registered id as argv[1].
 fn pciDriverForIdentity(identity: u64) ?[]const u8 {
     return switch (identity) {
-        xhci_pci_class => "usb-xhci-bus",
-        virtio_gpu_pci_class => "virtio-gpu",
+        xhci_pci_class => "/system/drivers/usb-xhci-bus",
+        virtio_gpu_pci_class => "/system/drivers/virtio-gpu",
         else => null,
     };
 }
@@ -67,8 +67,8 @@ fn pciDriverForIdentity(identity: u64) ?[]const u8 {
 /// nodes the kernel used to build). ps2-bus is a singleton that finds both its
 /// devices by hid once spawned, so keyboard and mouse map to the same name.
 fn hidDriverFor(hid: []const u8) ?[]const u8 {
-    if (std.mem.eql(u8, hid, "PNP0303")) return "ps2-bus"; // PS/2 keyboard
-    if (std.mem.eql(u8, hid, "PNP0F13")) return "ps2-bus"; // PS/2 mouse
+    if (std.mem.eql(u8, hid, "PNP0303")) return "/system/drivers/ps2-bus"; // PS/2 keyboard
+    if (std.mem.eql(u8, hid, "PNP0F13")) return "/system/drivers/ps2-bus"; // PS/2 mouse
     return null;
 }
 
@@ -95,9 +95,9 @@ fn usbDriverForIdentity(identity: u64) ?[]const u8 {
         @intFromEnum(usb_ids.mass_storage.Protocol.bulk_only),
     );
     return switch (identity) {
-        keyboard => "usb-hid-keyboard",
-        mouse => "usb-hid-mouse",
-        storage => "usb-storage",
+        keyboard => "/system/drivers/usb-hid-keyboard",
+        mouse => "/system/drivers/usb-hid-mouse",
+        storage => "/system/drivers/usb-storage",
         else => null,
     };
 }
@@ -429,7 +429,7 @@ fn onMessage(message: []const u8, reply: []u8, sender: u32, capability: ?runtime
         writeLine("/system/services/device-manager: hello from {s} (device {d})\n", .{ driver.name(), hello.device_id });
         // Resilience drill (V6): once, kill the virtio-gpu driver a moment after it hellos, so
         // the normal restart policy respawns it — the compositor must survive and re-attach.
-        if (test_scanout_restart_mode and !test_scanout_killed and std.mem.eql(u8, driver.name(), "virtio-gpu")) {
+        if (test_scanout_restart_mode and !test_scanout_killed and std.mem.eql(u8, driver.name(), "/system/drivers/virtio-gpu")) {
             test_scanout_killed = true;
             test_kill_pid = sender;
             test_kill_due_ns = system.clock() + 1_500_000_000;
@@ -498,7 +498,7 @@ fn onChildAdded(message: []const u8, reply: []u8, sender: u32) usize {
         // Only the xHCI reporter is the drill's victim — pci-bus also reports
         // now, and whichever finishes second must not trigger the kill.
         if (driverByProcess(sender)) |driver| {
-            if (std.mem.eql(u8, driver.name(), "usb-xhci-bus")) {
+            if (std.mem.eql(u8, driver.name(), "/system/drivers/usb-xhci-bus")) {
                 // Delayed, not immediate: the device-list scenario's subscriber
                 // needs a window to enumerate and subscribe before the events.
                 test_usb_killed = true;