chore: archive QuickNav and ZTools into reference folder (#345)

Copy QuickNav and ZTools source trees into reference/ for developer
reference during the UI/UX rework. These are plain directories (not
submodules) and are not included in the build.

- reference/quicknav/ — QuickNav addon source
- reference/ztools/ — ZTools addon source

Part of the UI/UX rework preparation. See #346.

reference/quicknav/InitGui.py

@@ -0,0 +1,37 @@
+import FreeCAD as App
+import FreeCADGui as Gui
+
+
+class QuickNavWorkbench(Gui.Workbench):
+    """Invisible workbench that installs QuickNav on load.
+
+    QuickNav does not replace the active workbench -- it layers on top.
+    Loading QuickNav installs the event filter and nav bar, then
+    immediately re-activates the previously active workbench.
+    """
+
+    MenuText = "QuickNav"
+    ToolTip = "Keyboard-driven command navigation"
+
+    def Initialize(self):
+        from quicknav.core import QuickNavManager
+
+        QuickNavManager.instance().install()
+        App.Console.PrintMessage("QuickNav workbench initialized\n")
+
+    def Activated(self):
+        from quicknav.core import QuickNavManager
+
+        QuickNavManager.instance().handle_workbench_activated()
+
+    def Deactivated(self):
+        pass
+
+    def GetClassName(self):
+        return "Gui::PythonWorkbench"
+
+
+Gui.addWorkbench(QuickNavWorkbench())
+
+# Eager command registration
+from quicknav.commands import QuickNav_Toggle  # noqa: F401