Strip Destination Select page from macOS pkg installer

Collapse the Velopack-generated distribution.xml to a single install
domain so macOS Installer skips Destination Select, leaving Apple's
minimum pages (Introduction, Install, Summary). Welcome/license/readme/
conclusion pages are already absent (no --inst* options passed).

scripts/guibuild.py

@@ -21,6 +21,7 @@ This script:
 import io
 import os
 import platform
+import re
 import shutil
 import stat
 import subprocess
@@ -249,8 +250,7 @@ def _dotnet_has_runtime(exe: Path) -> bool:
 
 
 def fetch_dotnet() -> str:
-    """Resolve a dotnet host with a modern (>= 8) runtime, bootstrapping one
-    into build/dotnet/ if none is found.
+    """Resolve a dotnet host with a modern (>= 8) runtime, bootstrapping one into build/dotnet/ if none is found.
 
     A plain `dotnet` may resolve to a runtime-only installation, and
     long-running services (CI runners) may carry a stale environment without
@@ -376,6 +376,8 @@ def build_velopack(version: str) -> Path:
         setup = next(iter(sorted(releases_dir.glob(f"*{artifact_ext}"))), None)
     if setup is None:
         raise RuntimeError(f"vpk produced no *{artifact_ext} in {releases_dir}")
+    if sys.platform == "darwin":
+        minimize_macos_installer(setup)
     artifact = (
         _REPO_ROOT
         / "build"
@@ -386,6 +388,28 @@ def build_velopack(version: str) -> Path:
     return artifact
 
 
+def minimize_macos_installer(pkg: Path) -> None:
+    """Strip the Destination Select page from the Velopack-generated pkg.
+
+    Velopack hardcodes two install domains (currentUserHome + localSystem) in
+    the distribution XML, which makes macOS Installer show a Destination
+    Select page. With a single domain that page is skipped, leaving Apple's
+    minimum: Introduction, Install, Summary. Installs go to /Applications as
+    before (the component pkg is non-relocatable with a fixed location).
+    """
+    expanded = pkg.with_name(pkg.stem + "-expanded")
+    shutil.rmtree(expanded, ignore_errors=True)
+    subprocess.run(["pkgutil", "--expand", str(pkg), str(expanded)], check=True)
+    dist_xml = expanded / "Distribution"
+    xml = dist_xml.read_text()
+    new_xml, count = re.subn(r"<domains [^>]*/>", '<domains enable_localSystem="true" />', xml)
+    if count != 1:
+        raise RuntimeError("Unexpected distribution.xml: <domains> not found")
+    dist_xml.write_text(new_xml)
+    subprocess.run(["pkgutil", "--flatten", str(expanded), str(pkg)], check=True)
+    shutil.rmtree(expanded)
+
+
 def read_version() -> str:
     """Read version via setuptools_scm (same logic as hatch-vcs)."""
     return setuptools_scm.get_version(root=str(_REPO_ROOT))