Initial commit: Schunix as it stands before the SchOS rename

An x86-64 operating system built from xv6, now largely rewritten: SMP,
a copy-on-write root filesystem (SchFS), PCI/USB/virtio drivers, a TTF
rasteriser, and a Linux-numbered syscall ABI.

No history before this point -- the tree was never under version control.
This commit exists so the rename that follows has something to undo to.

projects/schwm/README.md

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+# SchWM — the Schunix Window Manager
+
+Policy. Where windows go, which one has focus, what happens when you drag a
+title bar, how alt-tab behaves, what a window looks like at its edges.
+
+SchWM is a *client* of Schcom, not part of it. It talks the same protocol
+every other client does, plus a privileged extension that lets it position
+and stack surfaces it does not own. That extension is the entire difference
+between a window manager and an ordinary application.
+
+## Status
+
+Not started. Blocked on Schcom, which is blocked on the kernel — see
+`../schcom/README.md`.
+
+## Why it is separate from the compositor
+
+Merging them is the common shortcut and it is the one that hurts later.
+Compositing is mechanical and must never stall: it runs every frame and a
+mistake there is a frozen screen. Window management is policy, full of
+special cases and personal taste, and it changes constantly. Putting them in
+one process means every experiment with focus behaviour risks the thing that
+puts pixels on the screen.
+
+Keeping them apart also means SchWM can be restarted, replaced, or simply not
+run. A Schcom with no window manager should still show a full-screen client —
+that is a useful state to be able to reach when something is wrong.