Rename Schunix to SchOS; the kernel becomes SchIFT

Removes the "-unix" element and with it any trademark exposure to The
Open Group.

The split follows the ecosystem layout: SchOS is the system, and the
kernel has its own name. Kernel-identity strings are the only places
that take SchIFT -- uname(2) sysname, /proc/version, and the two licence
sentences that say "kernel" outright. That is what every Unix does here:
`uname -s` on Linux reports the kernel, not the distribution. Everything
a user reads as the product -- panic screen, boot menu, error prefixes,
docs, LICENSE, NOTICE -- is SchOS.

schunix.img is schos.img, the logo assets and the musl TLS patch are
renamed, and __SCHUNIX__ is __SCHOS__ (the define and the patch that
consumes it moved together).

Two things the rename broke, both found by the bootcheck suite:

  - shmtest wrote "SCHUNIX-MMAP-OK" with a hardcoded length of 15 and
    compared it back by hand-counted offsets (m[3]=='U', m[14]=='K').
    The shorter marker left the write running two bytes past the literal
    and the compare reading past the data, failing a file-backed mmap
    that was working correctly. Now written and compared through one
    constant with sizeof.
  - bootcheck asserted a 31-byte file after appending to
    "hello-from-schunix"; the shorter string makes it 29.

Both are the same mistake: a string literal whose length is written out
somewhere else. Full suite green -- base, Tty, Ps, Sock, Fb, Usb, Evdev.

ports/Makefile

@@ -1,5 +1,5 @@
 # SPDX-License-Identifier: Apache-2.0
-# Schunix ports — third-party software, one directory per port.
+# SchOS ports — third-party software, one directory per port.
 # All ports are permissive-licensed (MIT, BSD, 0BSD, Apache 2.0).
 #
 #   ports/musl/    libc — installs headers/libs to build/ports/musl/prefix
@@ -15,7 +15,7 @@
 # Ports that live in this directory but are deliberately not built by `make`.
 # Empty for now; the filter stays because the reason it existed will recur --
 # a port whose licence cannot be combined with Apache-2.0 can be kept here for
-# local testing but must never be built into a Schunix image.
+# local testing but must never be built into a SchOS image.
 NOTPORTS :=
 PORTS := $(filter-out $(NOTPORTS), \
            $(patsubst %/,%,$(sort $(dir $(wildcard */Makefile)))))

ports/mk/port.mk

@@ -1,5 +1,5 @@
 # SPDX-License-Identifier: Apache-2.0
-# Shared definitions for all Schunix ports.
+# Shared definitions for all SchOS ports.
 # Include this at the top of each port's Makefile:  include ../mk/port.mk
 #
 # Layout contract — a port directory contains ONLY hand-written files:

ports/mksh/Makefile

@@ -1,6 +1,6 @@
 # SPDX-License-Identifier: Apache-2.0
 # mksh (MirBSD Korn Shell) — permissive: https://www.mirbsd.org/mksh.htm
-# Installed as /bin/sh — Schunix standardizes on "sh" as the one shell name;
+# Installed as /bin/sh — SchOS standardizes on "sh" as the one shell name;
 # no ksh/dash/other aliases are installed or looked up by init.
 
 include ../mk/port.mk
@@ -10,7 +10,7 @@ MKSH_URL     := http://www.mirbsd.org/MirOS/dist/mir/mksh/mksh-$(MKSH_VERSION).t
 
 TARBALL := $(DISTDIR)/mksh-$(MKSH_VERSION).tgz
 
-CFLAGS  := -static -D__SCHUNIX__ -I$(MUSL)/include -fno-stack-protector
+CFLAGS  := -static -D__SCHOS__ -I$(MUSL)/include -fno-stack-protector
 LDFLAGS := -static -L$(MUSL)/lib -lc
 
 $(TARBALL): | $(DISTDIR)

ports/musl/Makefile

@@ -27,8 +27,8 @@ $(SRCDIR): $(TARBALL)
 # so creating it bumps that directory's mtime — making the directory forever
 # newer than the stamp it contains, and re-running this rule on every single
 # build. The second run then fails, because the patch does not apply twice.
-$(SRCDIR)/.patched: patches/0001-schunix-tls.patch | $(SRCDIR)
-	cd $(SRCDIR) && patch -p1 < $(CURDIR)/patches/0001-schunix-tls.patch
+$(SRCDIR)/.patched: patches/0001-schos-tls.patch | $(SRCDIR)
+	cd $(SRCDIR) && patch -p1 < $(CURDIR)/patches/0001-schos-tls.patch
 	touch $@
 
 $(BUILDDIR)/config.mak: $(SRCDIR)/.patched
@@ -37,7 +37,7 @@ $(BUILDDIR)/config.mak: $(SRCDIR)/.patched
 		--prefix=$(PREFIX) \
 		--disable-shared \
 		CC=$(CC) \
-		CFLAGS="-D__SCHUNIX__ -fno-stack-protector"
+		CFLAGS="-D__SCHOS__ -fno-stack-protector"
 
 $(BUILDDIR)/lib/libc.a: $(BUILDDIR)/config.mak
 	$(MAKE) -C $(BUILDDIR)

ports/musl/patches/0001-schos-tls.patch

@@ -1,13 +1,13 @@
-From: Schunix Project <kernel@schunix.org>
-Subject: [PATCH] schunix: TLS via global, mallocng decls, optional malloc tracing
+From: SchOS Project <kernel@schos.org>
+Subject: [PATCH] schos: TLS via global, mallocng decls, optional malloc tracing
 
 Three local changes to musl 1.2.5, kept in one patch because they are all
-"make musl work on Schunix" and share a lifetime.
+"make musl work on SchOS" and share a lifetime.
 
 1. arch/x86_64/pthread_arch.h, src/env/__init_tls.c - TLS.
-   Schunix's kernel saves/restores FS_BASE at the syscall boundary, so
+   SchOS's kernel saves/restores FS_BASE at the syscall boundary, so
    arch_prctl(ARCH_SET_FS) is safe from userspace. __get_tp() is redirected
-   through a global uintptr_t (__schunix_tp) set at the START of __init_tp(),
+   through a global uintptr_t (__schos_tp) set at the START of __init_tp(),
    before __set_thread_area() is called. The rest of __init_tp() runs
    normally so td->locale and the other pthread fields still initialise.
 
@@ -20,17 +20,17 @@ Three local changes to musl 1.2.5, kept in one patch because they are all
 
 3. src/malloc/mallocng/meta.h, malloc.c - diagnostics, inert by default.
    get_meta()/alloc_group() tracing that dumps group/meta pointers to fd 2,
-   entirely inside #ifdef SCHUNIX_MALLOC_DEBUG, which nothing defines. Kept
+   entirely inside #ifdef SCHOS_MALLOC_DEBUG, which nothing defines. Kept
    because this is the instrumentation that resolved the boot-crash
    investigation in docs/architecture/kernel-history.md section 1; build
-   with -DSCHUNIX_MALLOC_DEBUG to re-enable.
+   with -DSCHOS_MALLOC_DEBUG to re-enable.
 
 --- a/arch/x86_64/pthread_arch.h	2024-03-01 03:07:33.000000000 +0100
 +++ b/arch/x86_64/pthread_arch.h	2026-08-01 19:11:51.533102649 +0200
 @@ -1,8 +1,13 @@
-+#ifdef __SCHUNIX__
-+extern uintptr_t __schunix_tp;
-+static inline uintptr_t __get_tp() { return __schunix_tp; }
++#ifdef __SCHOS__
++extern uintptr_t __schos_tp;
++static inline uintptr_t __get_tp() { return __schos_tp; }
 +#else
  static inline uintptr_t __get_tp()
  {
@@ -47,18 +47,18 @@ Three local changes to musl 1.2.5, kept in one patch because they are all
  
  volatile int __thread_list_lock;
  
-+#ifdef __SCHUNIX__
-+uintptr_t __schunix_tp;
++#ifdef __SCHOS__
++uintptr_t __schos_tp;
 +#endif
 +
  int __init_tp(void *p)
  {
  	pthread_t td = p;
  	td->self = td;
-+	// Set __schunix_tp for __get_tp() before calling __set_thread_area.
++	// Set __schos_tp for __get_tp() before calling __set_thread_area.
 +	// The kernel now correctly saves/restores FS_BASE at the syscall boundary.
-+#ifdef __SCHUNIX__
-+	__schunix_tp = (uintptr_t)TP_ADJ(p);
++#ifdef __SCHOS__
++	__schos_tp = (uintptr_t)TP_ADJ(p);
 +#endif
  	int r = __set_thread_area(TP_ADJ(p));
  	if (r < 0) return -1;
@@ -82,20 +82,20 @@ Three local changes to musl 1.2.5, kept in one patch because they are all
  #include <limits.h>
  #include "glue.h"
  
-+#ifdef SCHUNIX_MALLOC_DEBUG
-+static void schunix_hex(char *out, uint64_t v) {
++#ifdef SCHOS_MALLOC_DEBUG
++static void schos_hex(char *out, uint64_t v) {
 +	static const char digits[] = "0123456789abcdef";
 +	for (int i = 15; i >= 0; i--) { out[i] = digits[v & 0xf]; v >>= 4; }
 +}
-+static void schunix_dbg(const char *tag, uint64_t a, uint64_t b, uint64_t c) {
++static void schos_dbg(const char *tag, uint64_t a, uint64_t b, uint64_t c) {
 +	char buf[128];
 +	int n = 0;
 +	buf[n++]='['; buf[n++]='D'; buf[n++]='B'; buf[n++]='G'; buf[n++]=']'; buf[n++]=' ';
 +	for (const char *p = tag; *p; p++) buf[n++] = *p;
 +	buf[n++]=' ';
-+	schunix_hex(buf+n, a); n += 16; buf[n++]=' ';
-+	schunix_hex(buf+n, b); n += 16; buf[n++]=' ';
-+	schunix_hex(buf+n, c); n += 16; buf[n++]='\n';
++	schos_hex(buf+n, a); n += 16; buf[n++]=' ';
++	schos_hex(buf+n, b); n += 16; buf[n++]=' ';
++	schos_hex(buf+n, c); n += 16; buf[n++]='\n';
 +	__syscall(SYS_write, 2, buf, n);
 +}
 +#endif
@@ -107,13 +107,13 @@ Three local changes to musl 1.2.5, kept in one patch because they are all
  	}
  	const struct group *base = (const void *)(p - UNIT*offset - UNIT);
  	const struct meta *meta = base->meta;
-+#ifdef SCHUNIX_MALLOC_DEBUG
-+	schunix_dbg("get_meta p", (uint64_t)p, (uint64_t)offset, (uint64_t)index);
++#ifdef SCHOS_MALLOC_DEBUG
++	schos_dbg("get_meta p", (uint64_t)p, (uint64_t)offset, (uint64_t)index);
 +	{
 +		volatile uint64_t *rawbase = (volatile uint64_t *)base;
-+		schunix_dbg("get_meta RAW reread base[0..2]", rawbase[0], rawbase[1], rawbase[2]);
++		schos_dbg("get_meta RAW reread base[0..2]", rawbase[0], rawbase[1], rawbase[2]);
 +	}
-+	schunix_dbg("get_meta base/meta/meta->mem", (uint64_t)base, (uint64_t)meta, (uint64_t)meta->mem);
++	schos_dbg("get_meta base/meta/meta->mem", (uint64_t)base, (uint64_t)meta, (uint64_t)meta->mem);
 +#endif
  	assert(meta->mem == base);
  	assert(index <= meta->last_idx);
@@ -124,9 +124,9 @@ Three local changes to musl 1.2.5, kept in one patch because they are all
  	m->last_idx = cnt-1;
  	m->freeable = 1;
  	m->sizeclass = sc;
-+#ifdef SCHUNIX_MALLOC_DEBUG
-+	schunix_dbg("alloc_group p/m/cnt", (uint64_t)p, (uint64_t)m, (uint64_t)cnt);
-+	schunix_dbg("alloc_group readback mem->meta", (uint64_t)m->mem, (uint64_t)m->mem->meta, (uint64_t)sc);
++#ifdef SCHOS_MALLOC_DEBUG
++	schos_dbg("alloc_group p/m/cnt", (uint64_t)p, (uint64_t)m, (uint64_t)cnt);
++	schos_dbg("alloc_group readback mem->meta", (uint64_t)m->mem, (uint64_t)m->mem->meta, (uint64_t)sc);
 +#endif
  	return m;
  }

ports/toybox/Makefile

@@ -1,6 +1,6 @@
 # SPDX-License-Identifier: Apache-2.0
 # toybox — 0BSD-licensed: https://landley.net/toybox/
-# Provides Schunix's core utilities (ls, cat, cp, mv, rm, mkdir, ...) as a
+# Provides SchOS's core utilities (ls, cat, cp, mv, rm, mkdir, ...) as a
 # single multicall binary, installed under sysroot/bin/ once per applet name.
 #
 # mkfs (tools/mkfs.c) doesn't understand symlinks or hardlink dedup — each
@@ -16,7 +16,7 @@ TOYBOX_SHA256  := ad88a921133ae2231d9f2df875ec0bd42af4429145caea7d7db9e02208a6fd
 
 TARBALL := $(DISTDIR)/toybox-$(TOYBOX_VERSION).tar.gz
 
-CFLAGS  := -static -D__SCHUNIX__ -I$(MUSL)/include -fno-stack-protector
+CFLAGS  := -static -D__SCHOS__ -I$(MUSL)/include -fno-stack-protector
 LDFLAGS := -static -L$(MUSL)/lib -lc
 
 # The applet list is not hard-coded any more: `toybox` with no arguments prints