Builder on Windows: opening the viewer draws panels over the viewer at (0,0) and builds the MO panel #255

9.0.0-alpha.10, Windows 10. Opening the viewer (Builder) for a calculation takes about 1.9 s, and every intermediate state is drawn. Findings from a 60 fps screen recording, with frame numbers counted from the click:

1. 0–10 (~0.15 s): the new Builder window is shown before its first paint, so it shows the Organizer behind it, then a white window, then the black viewer, then the molecule (~0.4 s).
2. ~50–100 (~0.9 s): panels are created as children of the frame at its top-left corner (0,0) and are drawn there, on top of the 3-D viewer, until the dock (wxAUI) moves them into place. In turn:
   • an empty "Viewer" frame;
   • a property panel with an empty choice box;
   • a panel whose choice box reads "MO".
     This is the "square in the top-left corner" seen on Windows. The yellow square in them is one of the panels' controls.
3. The MO panel is constructed during the open, although no layout shows the MOs pane by default any more (af9e0a9). 8d3b06a was meant to build a property panel only when it is on screen; this one is still built.
4. The right-hand column is rebuilt three times: first the tool panes, then property panes, then the Property index. The toolbar appears last, about 1.8 s after the click.

Proposed fix

• Create panels hidden, and show them only after AddPane and the AUI Update have placed them.
• Hold redrawing of the frame during the open (wxWindowUpdateLocker on the frame) and show the frame only after its first complete layout.
• Find which path still builds MoPanel (and any other panel not on screen) and keep it lazy.
• Settle the right-hand column's final set of panes before the first Update, so it is laid out once.
• Measure with tests/windows/framelog.ps1, plus a count of panels constructed during an open.

Related: #254 (the same redraw pattern in the Organizer).