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, 31 insertions, 0 deletions

diff --git a/ui/windows/settings_window.py b/ui/windows/settings_window.py
index cea7e5c..ae44c31 100644
--- a/ui/windows/settings_window.py
+++ b/ui/windows/settings_window.py
@@ -137,6 +137,24 @@ class SettingsWindow(QWidget):
         self._update_status_lbl.setWordWrap(True)
         lay.addRow("", self._update_status_lbl)
 
+        import sys as _sys
+        if _sys.platform.startswith(("win", "linux")):
+            assoc_row = QHBoxLayout()
+            self._assoc_btn = QPushButton("Register .labui Files")
+            self._assoc_btn.setObjectName("configButton")
+            self._assoc_btn.setToolTip(
+                "Associates .labui files with LabUI so double-clicking one\n"
+                "in the OS file browser opens it here."
+            )
+            self._assoc_btn.clicked.connect(self._register_file_association)
+            assoc_row.addWidget(self._assoc_btn)
+            assoc_row.addStretch()
+            lay.addRow("File Associations:", assoc_row)
+            self._assoc_status_lbl = QLabel("")
+            self._assoc_status_lbl.setObjectName("traceSource")
+            self._assoc_status_lbl.setWordWrap(True)
+            lay.addRow("", self._assoc_status_lbl)
+
         rst = QPushButton("Reset to Defaults"); rst.setObjectName("configButton")
         rst.clicked.connect(self._reset_to_defaults)
         lay.addRow("", rst)
@@ -390,6 +408,19 @@ class SettingsWindow(QWidget):
             except Exception as e:
                 QMessageBox.critical(self, "Update Failed", str(e))
 
+    def _register_file_association(self):
+        from core.updater import is_frozen
+        if not is_frozen():
+            self._assoc_status_lbl.setText("Not available outside the packaged app (dev mode).")
+            return
+
+        from core.file_association import register
+        err = register()
+        if err:
+            self._assoc_status_lbl.setText(f"Failed: {err}")
+        else:
+            self._assoc_status_lbl.setText("✓ .labui files now open with LabUI.")
+
     def _reset_to_defaults(self):
         reply = QMessageBox.question(
             self, "Reset Settings",