Carry project memory in the repo, with tools/memory-sync.sh

Claude Code keeps per-project memory at <home>/.claude/projects/<key>/,
where <key> is the project's absolute path with every separator and the
drive colon turned into a dash. That makes it both rename-fragile and
machine-specific, and this project has hit each of those once:

  - D:\DEV\Schunix -> D:\DEV\SchOS changed the key, and 43 memories were
    invisible until moved across by hand.
  - Development happens from Windows and from Linux, and each looks in a
    different place for the same checkout.

Committing .claude/memory/ fixes both -- git carries it across renames
and between hosts -- and `import` puts it wherever the local machine
expects. .claude/settings.local.json stays ignored: those are per-machine
permissions.

The colon maps to a dash rather than being dropped. Deleting it gives
D-DEV-SchOS, which matches nothing and silently finds zero memories; that
was the first attempt. On Git Bash the key comes from `cygpath -w`,
because Claude Code is a Windows program and sees D:\DEV\SchOS, not
/d/DEV/SchOS.

.claude/memory/schos-cross-platform-build.md

@@ -0,0 +1,58 @@
+---
+name: schos-cross-platform-build
+description: "The build and tools support Windows, Linux, macOS and BSD; clang everywhere, and the four host assumptions that used to break"
+metadata: 
+  node_type: memory
+  type: project
+  originSessionId: 9d8a2aef-bcf0-47a0-96c6-f706efab4a95
+  modified: 2026-08-09T12:26:54.787Z
+---
+
+**Nexoniarz develops from both Windows and Linux and switches between them**, so
+nothing in the build may assume a host. As of 2026-08-09 all four are supported:
+Windows (Git Bash/MSYS), Linux, macOS, and the BSDs. See
+[[schunix-build-environment]] for why WSL is not an option on the Windows box.
+
+**One toolchain, not two.** clang is a cross-compiler by construction, so a
+single LLVM install produces every target the tree needs — bare-metal ELF, the
+16/32-bit code below 1 MB, and Linux/musl userland — from any host. The Makefile
+picks clang+lld whenever both are on PATH; `USE_GNU=1` forces the GNU fallback.
+The old GNU branch had rotted: it passed `--no-warn-rwx-segments`, which is a
+**hard error on lld**, and lld is the default linker on FreeBSD and macOS. It
+also wanted a brewed `x86_64-elf-gcc` before a Mac could build at all.
+
+**Host tools use the host's own `cc`.** Only mingw needs naming explicitly, and
+only because clang defaults to an MSVC target there while `tools/mkfs.c` needs
+`<unistd.h>` and `<dirent.h>`.
+
+**The four things that were actually host-specific**, all fixed — worth
+recognising the pattern before adding a fifth:
+
+1. `<sys/sysmacros.h>` is glibc/musl only. macOS and the BSDs have no such
+   header and take `major()`/`minor()` from `<sys/types.h>`. Guarded on
+   `__linux__` now.
+2. `sha256sum -c -` exists on Linux and Git Bash only. macOS has `shasum -a
+   256`, FreeBSD/NetBSD `sha256`, OpenBSD `cksum -a sha256`. `tools/sha256check.sh`
+   tries all five and compares digests itself rather than trusting a `-c` flag,
+   whose input format also differs.
+3. `nproc` is coreutils — absent on macOS and BSD, where it is
+   `sysctl -n hw.ncpu`.
+4. **`Join-Path $root 'build\x'` produces a filename containing a backslash on
+   a Unix host.** PowerShell 7 runs on Linux/macOS/BSD, so the .ps1 tools are
+   usable there, but only with forward slashes throughout and QEMU found on
+   PATH instead of a hardcoded scoop location.
+
+**Do not blanket-replace backslashes in the .ps1 tools.** `bootcheck.ps1` sends
+`printf 'caf\303\251'` to the guest to test UTF-8; rewriting those octal escapes
+changes what the test asserts without failing it. The sweep is restricted to
+known directory prefixes for exactly this reason.
+
+**Ports do not build on Windows** — `make ports` skips with a message and the
+tree relies on `sysroot/` being pre-staged. Building musl/toybox/mksh from
+source needs a Linux host. That is a real reason to keep the Linux path working,
+not a theoretical one.
+
+**Unverified, and say so when it matters:** the Linux, macOS and BSD paths are
+written from documented behaviour and have **never been executed** — this
+machine has no WSL and no second host. Windows is the only host where the build
+and `tools/bootcheck.ps1` have actually been run green.