Add .labui file association — open by double-click, cross-platform

Windows/Linux self-register via core/file_association.py (winreg /
XDG .desktop+mime), triggered from a new Settings button since there's
no installer to do it at install time. macOS gets it at build time via
labui.spec's new BUNDLE() step (CFBundleDocumentTypes in Info.plist) —
that step also makes mac builds a real .app bundle for the first time,
not just a bare onedir folder. main.py gains a LabUIApplication
subclass to catch the macOS QFileOpenEvent (buffered if it arrives
before MainWindow exists) plus argv[1] handling for Windows/Linux.
ProfileButton.load_path() extracted so both paths share the same
load-and-apply logic as the existing file-dialog flow.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/ui/main_window.py b/ui/main_window.py
index 012d6f5..b632535 100644
--- a/ui/main_window.py
+++ b/ui/main_window.py
@@ -601,6 +601,11 @@ class MainWindow(QMainWindow):
 
     # ── Profile callbacks ─────────────────────────────────────────────────
 
+    def load_profile_path(self, path: str) -> bool:
+        """Load a .labui file from an explicit path — used when one is
+        opened from the OS (double-click / CLI argv), see main.py."""
+        return self._file_btn.load_path(path)
+
     def _profile_new(self):
         """Reset to a blank slate."""
         # Clear devices