Multi-select, context menu, section strikethrough, rename/duplicate presets

- Multi-select strips with click, Ctrl+click (toggle), Shift+click (range, same zone)
- Right-click selected strip: context menu with Cascade CC, Assign Channel, Deselect All
- Right-click unselected strip: clears all selections
- Selection status label shows count and type (faders/toggles/transport toggles)
- Rename preset button added to preset row
- Duplicate preset button auto-generates new UUID
- Layout panel section buttons show strikethrough when hidden, normal when visible
- Renamed Preset Browser to Instrument Browser in UI
- Transport strips wired for multi-select and context menu

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

faderwidget.py

@@ -206,6 +206,7 @@ class FaderWidget(QWidget):
         self.fader.valueChanged.connect(self.on_fader_moved)
         self.cc_spin.valueChanged.connect(self.on_cc_changed)
         self.on_select_callback = None
+        self.on_context_menu_callback = None
         self.hw_cc = None  # bound hardware CC number
         self.is_learning = False
         self.zone = None  # None, "left", or "right"
@@ -219,15 +220,25 @@ class FaderWidget(QWidget):
 
     def eventFilter(self, obj, event):
         if event.type() == QEvent.Type.MouseButtonPress:
-            if self.on_select_callback:
-                self.on_select_callback(self)
+            if event.button() != Qt.MouseButton.RightButton:
+                if self.on_select_callback:
+                    self.on_select_callback(self)
+        elif event.type() == QEvent.Type.ContextMenu:
+            if self.on_context_menu_callback:
+                self.on_context_menu_callback(self, event.globalPos())
+            return True
         return False
 
     def mousePressEvent(self, event):
-        if self.on_select_callback:
-            self.on_select_callback(self)
+        if event.button() != Qt.MouseButton.RightButton:
+            if self.on_select_callback:
+                self.on_select_callback(self)
         super().mousePressEvent(event)
 
+    def contextMenuEvent(self, event):
+        if self.on_context_menu_callback:
+            self.on_context_menu_callback(self, event.globalPos())
+
     def on_pickup_changed(self, state):
         self.pickup_mode = bool(state)
         if self.pickup_mode: