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infinite, and marks schwm/ and schde/ superseded: in Wayland the compositor is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

docs/architecture/devices.md

@@ -0,0 +1,104 @@
+# The device model
+
+How hardware gets found, claimed and used, and what the rest of the kernel sees
+of it.
+
+Writing a driver is [../guides/adding-a-driver.md](../guides/adding-a-driver.md).
+Moving drivers out of the kernel entirely is [../plan/hybrid.md](../plan/hybrid.md).
+
+---
+
+## One list of everything attached
+
+There is one list of everything attached, whatever bus found it:
+`include/device.h` and `kernel/dev/device.c`, readable at `/proc/devices`.
+
+```
+name      bus       class     driver    device
+kbd0      platform  input     ps2kbd    PS/2 keyboard
+mouse0    platform  input     ps2mouse  PS/2 mouse
+uart0     platform  other     uart8250  16550 serial port
+ide0      platform  storage   ide       ATA disk controller
+vga0      pci       display   vga       display controller
+```
+
+Before this there were two registries in `kernel/drivers/registry.c` — an array
+of PCI drivers and an array of USB drivers — with nothing that knew about both.
+That is sufficient for *binding* and useless for the three things wanted next.
+
+**Enumeration.** "What is in this machine, and what claimed it" had no answer
+covering a USB disk and a PCI display at once. A device manager is exactly that
+question.
+
+**Classes.** A compositor should ask for *the display* and not care whether that
+is the VBE framebuffer or virtio-gpu. Without a class every consumer hardcodes a
+driver, and adding the second driver means editing the consumers — which is how
+a framebuffer address ended up hardcoded in three places here once already.
+
+**A boundary for drivers that are not compiled in.** They have to attach
+somewhere that is not an array fixed at link time.
+
+Two vocabularies are kept deliberately separate: a device's **bus** is
+provenance (`platform`, `pci`, `usb`), its **class** is capability
+(`display`, `input`, `storage`, `net`, `bus`). A USB disk and a SATA disk are
+both `storage` despite sharing no numbering at all. Where a driver claims a
+device, the driver's opinion wins over the descriptor's: `struct usb_driver` has
+a `devclass` field separate from the USB interface class, because the descriptor
+says what the device *claims* to be and the driver knows what it *made* of it.
+
+It is a flat list with a bus tag, **not** a device tree. Nothing yet needs to
+walk a hierarchy, and a tree nobody traverses is just a harder list. Hot-unplug
+would need more; the `in_use` flag is the hook.
+
+Platform devices are registered in one place
+(`platform_register_devices()` in `registry.c`) rather than inside each driver's
+init, for the same reason the driver arrays are written out by hand: a list you
+can read beats a list assembled by side effects.
+
+---
+
+## Linux drivers
+
+**Decided 2026-08-08.** Linux drivers are not shipped with SchOS and never
+will be. The user may install one on their own machine, through a device
+manager or equivalent, and SchOS will load it.
+
+The licensing reasoning matters and is worth stating exactly, because it is
+easy to get wrong in both directions:
+
+- **Distribution is what triggers the GPL.** Shipping a GPL-2.0-only driver in
+  an Apache-2.0 image is what cannot be done — see [../licensing.md](../licensing.md)
+  §2. A user obtaining a driver themselves and loading it on their own machine
+  is their act, not ours, and is not a distribution by us.
+- **Implementing a loader is not copying.** Writing support for a module format
+  and a driver ABI from published documentation produces our own work. It is a
+  clean-room implementation, and it stays one only if it is written from
+  documentation rather than transcribed from Linux source. Reading Linux to
+  understand *hardware* is fine; translating its code is not, whatever the
+  identifiers say.
+
+So the rule for this subsystem is the same as everywhere else in the tree: the
+loader is ours and Apache-2.0, what it loads is the user's business, and nothing
+GPL ever enters an image we build. `RAMDISK_EXCLUDE` and `NOTPORTS` are the
+existing mechanisms for keeping that true mechanically rather than by intention.
+
+---
+
+
+---
+
+## What it does not do
+
+- **It is a flat list, not a device tree.** There is no parent/child nesting,
+  only a bus tag. Nothing yet needs to walk a hierarchy, and a tree nobody
+  traverses is just a harder list.
+- **No hot-plug.** Devices are registered at boot and never removed; the
+  `in_use` flag is the hook a hot-unplug path would need, and nothing sets it
+  for that purpose.
+- **`NDEVICE` is 32**, compile-time, like every other table in the kernel.
+- **Drivers are fixed at link time.** There is no module loader, and nothing can
+  be installed after the build — the class vtable is the attachment point a
+  loader would use, and it is the only part that exists.
+- **Only two class vtables are defined**: `display_ops` and `netdev_ops`.
+  Storage and input devices appear in the list with `ops = 0` and are reached
+  through their own subsystems instead.