macOS: guest agent, online templates, virtio-fs shares, persistent home volume

Apple's built-in QEMU guest agent (AppleQEMUGuestAgent, launched by launchd
when a virtio console port org.qemu.guest_agent.0 appears; guest-exec as root)
is attached by vmix run --macos and the NixOS module. AppleVirtIO.kext on x86
Tahoe drives virtio-fs, block, console, input, net — verified in QEMU.

- customizeImage: `bootScript` — online step through the guest agent (driver
  mode qga): boot the image, run the script as root with the VMIX volume, shut
  down through the agent. `as_user` runs commands in the logged-in session.
- templates.software: pkg/app (offline in the PE), script/homebrew (online).
- templates.profile.settings: widgets, wallpaper (pinned desktoppr — Apple
  Events need TCC consent that a headless session cannot give), dock apps,
  autohide, dark mode, hidden files.
- generalize: persistHome (fstab LABEL=vmix-home /Users), hideWidgets offline.
- formatVolume: formats a blank disk image as APFS by booting the PE (~35 s);
  idempotent.
- NixOS module: macos.guestAgent (/run/vmix/qga-<name>.sock), shares via
  virtiofsd + vhost-user-fs (Apple automount tag for the first share, others
  mounted through the agent), macos.homeDisk (created + formatted on first
  start, virtio-blk), SPICE keeps -vga vmware for macOS.
- CLI: vmix run --macos --share DIR --home FILE --qga PATH.
- qemu.nix helpers; README section.

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

lib/images/macos/templates/software/default.nix

@@ -0,0 +1,51 @@
+# Software installation templates.
+#   pkg    — install a flat/distribution .pkg offline from the PE (`installer -target`)
+#   app    — copy an .app bundle (from a directory or zip) into /Applications offline
+#   script — run a shell script as root on the booted image (network available)
+{ pkgs, lib, ... }:
+rec {
+  pkg = { name, src, choices ? null }: {
+    name = "pkg-${name}";
+    files = [ { source = src; name = "${name}.pkg"; } ]
+      ++ lib.optional (choices != null) { source = choices; name = "${name}.choices.xml"; };
+    script = ''
+      echo "vmix: installing ${name}.pkg into $SYS"
+      installer -verboseR -pkg "$V/${name}.pkg" -target "$SYS" \
+        ${lib.optionalString (choices != null) ''-applyChoiceChangesXML "$V/${name}.choices.xml"''} \
+        || pe_fail "installer ${name}.pkg"
+    '';
+  };
+
+  app = { name, src }: {
+    name = "app-${name}";
+    files = [ { source = src; name = "${name}.app"; } ];
+    script = ''
+      echo "vmix: copying ${name}.app to $DATA/Applications"
+      mkdir -p "$DATA/Applications"
+      rm -rf "$DATA/Applications/${name}.app"
+      ditto "$V/${name}.app" "$DATA/Applications/${name}.app" || pe_fail "ditto ${name}.app"
+      chown -R 0:80 "$DATA/Applications/${name}.app"
+      xattr -dr com.apple.quarantine "$DATA/Applications/${name}.app" 2>/dev/null || true
+    '';
+  };
+
+  script = { name, script, files ? [], network ? true }: {
+    name = "script-${name}";
+    inherit files network;
+    bootScript = script;
+  };
+
+  # Homebrew (needs network; installs for the console user or the given user)
+  homebrew = { user ? null, formulae ? [], casks ? [] }: {
+    name = "homebrew";
+    bootScript = ''
+      U=${if user == null then "$CONSOLE_USER" else user}
+      [ -n "$U" ] || { echo "vmix: no user to install Homebrew for"; exit 1; }
+      launchctl asuser "$(id -u "$U")" sudo -u "$U" env NONINTERACTIVE=1 \
+        /bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)" || exit 1
+      B=/usr/local/bin/brew
+      ${lib.optionalString (formulae != []) ''launchctl asuser "$(id -u "$U")" sudo -u "$U" $B install ${lib.escapeShellArgs formulae} || exit 1''}
+      ${lib.optionalString (casks != []) ''launchctl asuser "$(id -u "$U")" sudo -u "$U" $B install --cask ${lib.escapeShellArgs casks} || exit 1''}
+    '';
+  };
+}