C6: update docs for the library/kernel + client split

Rewrote the repository-layout and driver-model docs to describe the new tree —
library/kernel (the kernel32-style system library: syscall surface split by
concern), library/device (mmio/model/pci/usb/acpi/driver/block), library/client
(display, input service clients), library/protocol (wire contracts) — and swept
the reference docs off the retired runtime shim:

  runtime.system.*  -> logging.* / time.* / process.* / memory.*
  runtime.dma.* / runtime.shared_memory.* / runtime.allocator -> memory.*
  runtime.ipc/process/time/service/Thread/block/display/input -> the module name
  runtime.device / runtime.device_manager -> driver
  library/runtime/<file>.zig -> its new home (kernel/ client/ device/)

docs/README.md (repository layout + source map), docs/driver-model.md (the module
graph + import lists), and the concern/reference docs (ipc, threading, timers,
logging, power, process-lifecycle, device-manager, display, vdso, sysv, drivers,
input, vfs-protocol, coding-standards, ...) now reflect the split. "runtime" that
remains is the userspace-library *concept*, which is still accurate.

The historical plan docs (display-plan, display-v2-plan, threading-plan) and the
zig-self-hosting design note are left as point-in-time snapshots.

docs/power.md

@@ -17,7 +17,7 @@ What subscribers want is not: *the lid closed* means the same thing regardless o
 who noticed. So the surface is **domain-named**. There is a `power-protocol`
 module and a well-known `ServiceId.power = 5`; on x86 the **acpi service**
 registers it, and on ARM a PSCI/mailbox service will register the *same* id.
-Subscribers call `runtime.ipc.lookup(.power)` and never learn which firmware they
+Subscribers call `ipc.lookup(.power)` and never learn which firmware they
 are on — the neutrality the whole [discovery](discovery.md) migration exists to
 preserve, carried one layer up into a running-system surface.
 
@@ -75,7 +75,7 @@ notifications, the lifecycle **signals** it can receive (`terminate`), and the
 On a `power_button` event or a `terminate` signal, init:
 
 1. logs that it is shutting down,
-2. runs the standard stop sequence — `runtime.process.stop(child, deadline,
+2. runs the standard stop sequence — `process.stop(child, deadline,
    endpoint)` — over its children **in reverse spawn order**, so the VFS stops
    last (other services may flush through it), each child getting the
    *terminate → deadline → kill* escalation from