fix: replace QFontComboBox with QComboBox, move Preferences to Edit menu

- Replace QFontComboBox with static QComboBox (10 monospace fonts) in
  preferences_dialog.ui to eliminate recursive-repaint SIGSEGV in xvfb.
  QFontComboBox renders all system font previews via a custom delegate,
  causing paint re-entrancy under headless compositors.
- Remove QFontComboBox import from preferences_dialog.py; use QComboBox
  setCurrentText/currentText instead of setCurrentFont/currentFont().
- Move actionPreferences from menuFile to menuEdit in main_window.ui;
  Edit menu was previously empty (design spec requires Preferences there).
- _on_action_preferences: call _apply_preferences() once after exec()
  returns rather than via live preferences_changed signal. Connecting
  _apply_preferences during exec() causes app.setPalette() + setRootIndex()
  to trigger recursive repaints inside the modal event loop → SIGSEGV.
  Cancel leaves QSettings unchanged, so post-exec _apply_preferences() is
  a safe no-op.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: chrisdpurcell

src/views/main_window.py

@@ -458,10 +458,17 @@ def _on_action_about(self) -> None:
         )
 
     def _on_action_preferences(self) -> None:
-        """Open the Preferences dialog; apply settings live on Apply/OK."""
+        """Open the Preferences dialog; apply settings after dialog closes.
+
+        Preferences are applied once after exec() returns rather than live via
+        preferences_changed signal. Connecting _apply_preferences during exec()
+        causes app.setPalette() + setRootIndex() to trigger recursive repaints
+        inside the modal event loop → SIGSEGV. Cancel leaves QSettings unchanged
+        so _apply_preferences() is a no-op after Cancel.
+        """
         prefs = PreferencesDialog(self.ui)
-        prefs.preferences_changed.connect(self._apply_preferences)
         prefs.exec()
+        self._apply_preferences()
 
     # ---------------------------------------------------------- merge tab handlers
 

src/views/preferences_dialog.py

@@ -10,13 +10,12 @@
 import os
 
 from PySide6.QtCore import QDir, QFile, QObject, QSettings, Signal
-from PySide6.QtGui import QFont
 from PySide6.QtUiTools import QUiLoader
 from PySide6.QtWidgets import (
     QCheckBox,
+    QComboBox,
     QDialog,
     QFileDialog,
-    QFontComboBox,
     QLineEdit,
     QPushButton,
     QRadioButton,
@@ -89,7 +88,7 @@ def _load_ui(self, parent: QWidget | None) -> None:
         self.dialog: QDialog = loaded  # type: ignore[assignment]
 
         self._font_family_combo = _require(
-            self.dialog.findChild(QFontComboBox, "fontFamilyComboBox"),
+            self.dialog.findChild(QComboBox, "fontFamilyComboBox"),
             "fontFamilyComboBox",
         )
         self._font_size_spin = _require(
@@ -136,8 +135,8 @@ def _connect_signals(self) -> None:
     def _load_from_settings(self) -> None:
         """Populate widgets from QSettings (falls back to DEFAULTS for missing keys)."""
         settings = QSettings()
-        self._font_family_combo.setCurrentFont(
-            QFont(str(settings.value(KEY_FONT_FAMILY, DEFAULTS[KEY_FONT_FAMILY])))
+        self._font_family_combo.setCurrentText(
+            str(settings.value(KEY_FONT_FAMILY, DEFAULTS[KEY_FONT_FAMILY]))
         )
         self._font_size_spin.setValue(
             int(settings.value(KEY_FONT_SIZE, DEFAULTS[KEY_FONT_SIZE]))
@@ -158,7 +157,7 @@ def _load_from_settings(self) -> None:
     def _write_to_settings(self) -> None:
         """Persist current widget values to QSettings."""
         settings = QSettings()
-        settings.setValue(KEY_FONT_FAMILY, self._font_family_combo.currentFont().family())
+        settings.setValue(KEY_FONT_FAMILY, self._font_family_combo.currentText())
         settings.setValue(KEY_FONT_SIZE, self._font_size_spin.value())
         settings.setValue(KEY_WORD_WRAP, self._word_wrap_cb.isChecked())
         settings.setValue(KEY_LINE_NUMBERS, self._line_numbers_cb.isChecked())

src/views/ui/main_window.ui

@@ -960,14 +960,14 @@
     <addaction name="actionOpen"/>
     <addaction name="actionSave"/>
     <addaction name="actionSave_as"/>
-    <addaction name="actionPreferences"/>
     <addaction name="separator"/>
     <addaction name="actionQuit"/>
    </widget>
    <widget class="QMenu" name="menuEdit">
     <property name="title">
      <string>Edit</string>
     </property>
+    <addaction name="actionPreferences"/>
    </widget>
    <widget class="QMenu" name="menuHelp">
     <property name="title">

src/views/ui/preferences_dialog.ui

@@ -29,13 +29,23 @@
          </widget>
         </item>
         <item>
-         <widget class="QFontComboBox" name="fontFamilyComboBox">
+         <widget class="QComboBox" name="fontFamilyComboBox">
           <property name="sizePolicy">
            <sizepolicy hsizetype="Expanding" vsizetype="Fixed">
             <horstretch>1</horstretch>
             <verstretch>0</verstretch>
            </sizepolicy>
           </property>
+          <item><property name="text"><string>Monospace</string></property></item>
+          <item><property name="text"><string>Noto Sans Mono</string></property></item>
+          <item><property name="text"><string>DejaVu Sans Mono</string></property></item>
+          <item><property name="text"><string>Liberation Mono</string></property></item>
+          <item><property name="text"><string>Courier New</string></property></item>
+          <item><property name="text"><string>Consolas</string></property></item>
+          <item><property name="text"><string>Inconsolata</string></property></item>
+          <item><property name="text"><string>Source Code Pro</string></property></item>
+          <item><property name="text"><string>Fira Code</string></property></item>
+          <item><property name="text"><string>JetBrains Mono</string></property></item>
          </widget>
         </item>
         <item>