docs: four directories, and a rule for when a thing leaves the roadmap

docs/ was ten files where a plan, a description, a guide and a bug report all
sat next to each other. It is now architecture/ (what SchOS is), plan/ (what it
will be), guides/ (how to work on it) and history/ (why it is like this), with
an index that states the one rule holding it together: when something is
finished it moves from plan/ to architecture/ and is rewritten as a description
of the thing rather than a record of building it.

A ticked checkbox says the work happened. It does not say what the work
*produced*, and six months later the checkbox is all that is left. The network
stack proved the point: finished, verified end to end, and for a month the only
description of it anywhere was a checkbox four levels of indentation deep.

So roadmap.md went from 534 lines to 181 -- nothing deleted, the done work
graduated. Seven subsystems that were finished and undescribed now have
descriptions: boot, kernel, syscalls, filesystem, networking, graphics, usb,
init. Every one ends with "What it does not do", which is the section that pays;
a document listing only strengths is marketing, and the reader who needs it most
is the one about to trip over a limitation nobody wrote down.

schfs.md still opened with "phases 1 through 3 1/2 are done, phase 4 is next"
long after all five had landed. It is a description now, with the phase record
and the hard-won bugs moved to history/.

Three corrections found on the way, all load-bearing:

  * projects/schcom/README.md claimed SCM_RIGHTS was done. There is no
    sendmsg/recvmsg in the kernel at all, and an entire GUI plan rested on it.
  * The root README said "No TCP/IP" months after the stack landed.
  * history/kernel.md sec.7 was marked "in progress" on a problem that process
    groups solved.

Also adds plan/1.0.md, which draws a finish line so the open list stops being
infinite, and marks schwm/ and schde/ superseded: in Wayland the compositor is
the window manager, so that split dissolves rather than being abandoned.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VQ7Qx8E1q1M1bbCq8QLHS2

kernel/arch/x86_64/mp.c

@@ -146,7 +146,7 @@ mpinit(void)
   // interrupt assignments. So ncpu is 1 on QEMU no matter what, and SMP is
   // silently never exercised there.
   //
-  // See docs/roadmap.md "Known broken" -- this is half of the SMP bug, and the
+  // See docs/architecture/boot.md -- this is half of the SMP bug, and the
   // reason the other half (AP startup triple-faulting) cannot be reproduced
   // under QEMU until the MADT is parsed.
   cprintf("Seems we are SMP, ncpu = %d\n",ncpu);

kernel/arch/x86_64/trap.c

@@ -133,7 +133,7 @@ trap(struct trapframe *tf)
     // General-purpose register dump. This used to be followed by ~25 lines
     // that walked musl's mallocng group/meta structures out of rax/rdi and
     // dumped the user stack -- scaffolding for the boot-crash investigation
-    // recorded in docs/architecture/kernel-history.md section 1. That
+    // recorded in docs/history/kernel.md section 1. That
     // investigation is closed and the underlying kernel bugs are fixed, so
     // the allocator-specific part is gone; the registers stay, since they are
     // useful for any fault.