macOS Tahoe VM images (OpenCore/QEMU), Apple-ID compatible, VNC

Add a macOS image pipeline mirroring the Windows one: unattended install,
generalization and user creation, driven end to end in QEMU on a KVM host.

lib/images/macos:
- makeOpenCore: OSX-KVM OpenCore ESP with a config.plist rewritten per image —
  SMBIOS model + serial/MLB (macserial) + UUID + ROM=en0 MAC (built-in NIC pinned
  to PciRoot(0x0)/Pci(0x12,0x0)) for Apple ID / iMessage / App Store; boot disk;
  OpenCore self-entry hidden. ident.nix derives MAC+UUID from a seed so the NixOS
  module and CLI know the NIC MAC at eval time.
- makeImage: one QEMU session driven by vm-driver.py (QMP + screenshot settle
  detection + OCR of the menu bar) — boots the recovery via OpenCore, opens
  Terminal (Ctrl-F2 -> Utilities -> Terminal), types the bootstrap command;
  vmix-install.sh erases the disk as APFS, lays down the host-extracted installer
  app skeleton + a byte-exact SharedSupport.dmg (raw disk mapped to that byte range
  of the pkg, dd'd in — Recovery's xar truncates an 18 GB member), runs
  startosinstall with the vmix agent pkg. OpenCore is then copied into the image's
  ESP so it boots standalone with OVMF.
- customizeImage / templates: boot the image with a FAT-then-HFS+ VMIX volume; the
  vmix agent (LaunchDaemon) runs a script as root, records status and powers off —
  the macOS counterpart of Windows Audit Mode. generalize creates the admin user +
  auto-login (kcpassword), suppresses Setup Assistant, sets hostname/timezone,
  grows APFS, and assigns a fresh SMBIOS identity. Templates: noUpdates,
  performance, remoteAccess (ssh + screen sharing).
- fetchRecovery: Apple recovery BaseSystem, retried until the pinned Tahoe build
  (osrecovery load-balances Sequoia/Tahoe during the rollout). makeAgentPkg builds
  a distribution flat pkg on Linux (xar+bom+cpio) for startosinstall --installpackage.

CLI: vmix build/copy/run for macOS (run --macos --vnc, reads the image's MAC from
its ESP), and a `vmix macserial` helper. NixOS module: disks.os.file carrying
_vmixOsType="macos" auto-enables the macOS QEMU profile (AppleSMC+OSK, Skylake
CPU spoof, AHCI system disk, VMware SVGA, pinned NIC); macos.{enable,cpu,mac}.

Status: proven through the installer prepare phase (SharedSupport.dmg mounts,
version 26.6.2 read, SU catalog loads). Two blockers remain, documented in
lib/images/macos/README.md: (1) startosinstall's OSISVerifyBaseSystemOperation
rejects the byte-identical plain-UDIF SharedSupport as "pkgdmg missing a footer"
in this Tahoe recovery/VM; (2) Apple's CDN unreliably serves the Tahoe recovery
during rollout (self-hosting the verified BaseSystem is the robust fix).

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XsESshRCoBoUVWV9qKURUF

lib/images/macos/helpers/installerPayload.nix

@@ -0,0 +1,28 @@
+# Take apart InstallAssistant.pkg on Linux:
+#   installer-app.tar  "Install macOS <name>.app" skeleton (Payload, pbzx+cpio)
+#   installer.json     byte offsets of SharedSupport.dmg inside the pkg
+#   app-name           e.g. "Install macOS Tahoe.app"
+# The 18 GB SharedSupport.dmg is never copied on the host; makeImage exposes that
+# byte range of the pkg as a raw disk and the recovery script copies it into the app.
+{ pkgs, lib, ... }:
+{ name, pkg }:
+pkgs.runCommand "${name}-installer-payload" {
+  nativeBuildInputs = with pkgs; [ xar pbzx cpio python3 gnutar ];
+} ''
+  mkdir -p $out
+  xar --dump-toc=toc.xml -f ${pkg}
+  python3 ${./xar-toc.py} toc.xml ${pkg} > $out/installer.json
+  grep -q '"SharedSupport.dmg"' $out/installer.json || { echo "no SharedSupport.dmg in pkg"; exit 1; }
+  grep -A4 '"SharedSupport.dmg"' $out/installer.json | grep -q '"encoding": "application/octet-stream"' \
+    || { echo "SharedSupport.dmg is compressed inside the xar, cannot map it as a disk"; exit 1; }
+
+  echo "=== vmix: extracting installer app skeleton ==="
+  xar -x -f ${pkg} Payload
+  mkdir root
+  (cd root && pbzx -n ../Payload | cpio -idm --quiet)
+  APP=$(ls root/Applications | grep -E '^Install macOS.*\.app$' | head -1)
+  [ -n "$APP" ] || { echo "installer app not found in Payload"; ls -R root | head; exit 1; }
+  echo "$APP" > $out/app-name
+  tar -C root/Applications -cf $out/installer-app.tar "$APP"
+  ls -la $out
+''