kernel: a refusal names its rule, and two bounds stop failing open

An AMD Ryzen booted to a working compositor with no USB and no storage,
and the log said only "register refused". A tree-wide audit of every
compile-time ceiling followed: 235 of them, 139 on quantities the machine
or a file decides rather than us, 5 documented anywhere, 171 silent when
reached. docs/fixed-bounds-audit.md has the inventory.

Errno attribution. The errno space was split between the kernel and the
envelope, free to drift; it is now one list in system/abi.zig, restated on
both sides, with a comptime check in library/device/driver where the two
halves are visible. device_register's six refusals and device_claim's three
are distinct codes, so a bus driver can say which rule stopped it, and
BadParent splits into NoSuchParent and NotYourParent. pci-bus reconciles
found against registered instead of counting refused functions as found.

Idempotency ordering. The child cap was checked before the identity match,
so a restarted bus was refused its own devices — the supervision restart the
system leans on ratcheted toward a degraded machine. A re-registration
consumes no slot and is now admitted first.

IOMMU fail-closed. confineDevice returned success for a device id past the
confinement table, leaving the device outside every domain while the caller
believed it confined — unreachable only while ids stop at 64, which both the
inventory move and a hardware-reported domain count would change. It refuses
now, and the coupling to the broker's device cap is a comptime assert rather
than a sentence in a comment.

PCI apertures. The bridge's MMIO apertures are derived from the holes in the
firmware memory map, and the derivation copied sub-4 GiB entries into a
fixed [64] array and skipped the rest. A skipped region is not merely lost:
the gap finder concludes it is free, so a real machine's 60-200 entry map
yields an aperture over live RAM, and containment then admits a child BAR
covering kernel memory. Rewritten to walk the map in place, with the hole
finder extracted as a pure function and driven by a synthetic 100-entry map
in a new test case. Both new tests were verified to fail on the old code.

parameters.zig gains the rationale it was missing and loses a stale sentence
pointing at the wrong file; vdso.md documents the errno space, including
EPEER, which had no written meaning anywhere.

docs/os-development/bounds.md is how a ceiling is declared from here.
docs/bounds-track-plan.md is the plan to remove the ones we invented.

Suite 114 -> 115.

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

@@ -173,10 +173,10 @@ fn initialise(endpoint: ipc.Handle) bool {
     if (!channel.bindPatiently("usb-transfer", endpoint))
         _ = logging.write("/system/drivers/usb-xhci-bus: /protocol/usb-transfer is another controller's; serving mine unnamed\n");
 
-    if (!device.claim(controller_id)) {
-        std.log.info("unable to claim controller device {d}", .{controller_id});
+    device.claim(controller_id) catch |e| {
+        std.log.warn("unable to claim controller device {d}: {s}", .{ controller_id, @errorName(e) });
         return false;
-    }
+    };
 
     // Fetch our own descriptor back for the controller's resources.
     const buffer = memory.allocator().alloc(device.DeviceDescriptor, 64) catch {
@@ -522,8 +522,8 @@ fn reportInterface(manager: ipc.Handle, port: u32, interface: library.InterfaceI
     const hid_text = std.fmt.bufPrint(&hid_buffer, "P{d}I{d}", .{ port, interface.number }) catch "";
     descriptor.hid_len = hid_text.len;
     @memcpy(descriptor.hid[0..hid_text.len], hid_text);
-    const registered = device.register(controller_id, &descriptor) orelse {
-        std.log.info("register refused for port {d} interface {d}", .{ port, interface.number });
+    const registered = device.register(controller_id, &descriptor) catch |e| {
+        std.log.warn("register refused for port {d} interface {d}: {s}", .{ port, interface.number, @errorName(e) });
         return null;
     };