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/makeAgentPkg.nix

@@ -0,0 +1,75 @@
+# Distribution-style flat package (xar + bom + cpio, built on Linux) for
+# `startosinstall --installpackage`: installs the vmix agent LaunchDaemon and
+# marks Setup Assistant as done so the first boot lands on loginwindow.
+{ pkgs, lib, ... }:
+{ version ? "1.0" }:
+let
+  id = "ch.vmix.agent";
+  # nixpkgs' bomutils aborts under _FORTIFY_SOURCE
+  bomutils = pkgs.bomutils.overrideAttrs (_: { hardeningDisable = [ "fortify" ]; });
+  postinstall = pkgs.writeText "postinstall" ''
+    #!/bin/sh
+    # $3 = target volume
+    T="$3"
+    mkdir -p "$T/private/var/db"
+    touch "$T/private/var/db/.AppleSetupDone"
+    chown root:wheel "$T/private/var/db/.AppleSetupDone"
+    chmod 755 "$T/Library/vmix/agent.sh"
+    chown -R root:wheel "$T/Library/vmix" "$T/Library/LaunchDaemons/${id}.plist"
+    exit 0
+  '';
+in
+pkgs.runCommand "vmix-agent-${version}.pkg" {
+  nativeBuildInputs = [ pkgs.xar bomutils pkgs.cpio pkgs.gzip ];
+} ''
+  mkdir -p root/Library/LaunchDaemons root/Library/vmix scripts flat/vmix-agent.pkg
+  cp ${../guest/agent.sh} root/Library/vmix/agent.sh
+  cp ${../guest/ch.vmix.agent.plist} root/Library/LaunchDaemons/${id}.plist
+  chmod 755 root/Library/vmix/agent.sh
+  chmod 644 root/Library/LaunchDaemons/${id}.plist
+  cp ${postinstall} scripts/postinstall
+  chmod 755 scripts/postinstall
+
+  NFILES=$(find root | wc -l)
+  KBYTES=$(du -sk root | cut -f1)
+  (cd root && find . | cpio -o --format odc --owner 0:0 --quiet | gzip -c > ../flat/vmix-agent.pkg/Payload)
+  (cd scripts && find . | cpio -o --format odc --owner 0:0 --quiet | gzip -c > ../flat/vmix-agent.pkg/Scripts)
+  mkbom -u 0 -g 80 root flat/vmix-agent.pkg/Bom
+
+  cat > flat/vmix-agent.pkg/PackageInfo <<XML
+  <?xml version="1.0" encoding="utf-8"?>
+  <pkg-info overwrite-permissions="true" relocatable="false" identifier="${id}" postinstall-action="none" version="${version}" format-version="2" generated-by="vmix" auth="root">
+    <payload installKBytes="$KBYTES" numberOfFiles="$NFILES"/>
+    <bundle-version/>
+    <upgrade-bundle/>
+    <update-bundle/>
+    <atomic-update-bundle/>
+    <strict-identifier/>
+    <relocate/>
+    <scripts>
+      <postinstall file="./postinstall"/>
+    </scripts>
+  </pkg-info>
+  XML
+  cat > flat/Distribution <<XML
+  <?xml version="1.0" encoding="utf-8"?>
+  <installer-gui-script minSpecVersion="1">
+    <title>vmix agent</title>
+    <options customize="never" require-scripts="false" hostArchitectures="x86_64,arm64" rootVolumeOnly="true"/>
+    <product id="${id}" version="${version}"/>
+    <choices-outline>
+      <line choice="default">
+        <line choice="${id}"/>
+      </line>
+    </choices-outline>
+    <choice id="default"/>
+    <choice id="${id}" visible="false">
+      <pkg-ref id="${id}"/>
+    </choice>
+    <pkg-ref id="${id}" version="${version}" onConclusion="none" installKBytes="$KBYTES">#vmix-agent.pkg</pkg-ref>
+  </installer-gui-script>
+  XML
+  sed -i 's/^  //' flat/vmix-agent.pkg/PackageInfo flat/Distribution
+  (cd flat && xar --compression none -cf $out Distribution vmix-agent.pkg)
+  xar -t -f $out
+''