developer_panel: OnUpdated rebuilds the visualizers on every instance

A definition update rebuilds each instance's parm interface and leaves its
visualizers pointing at the old parms; the next write to one -- any tab
callback, even the Enable checkbox -- segfaults Houdini 22.0.429 in
VIS_Table::writeMount* (twice on 2026-09-15). Rebuild, which destroys and
recreates them, is the one safe write, so the OnUpdated event script now
schedules it on the next event-loop tick for every instance instead of
relying on the user to press the button before touching a tab.

The old script referenced a child node that never existed.

Verified in a shadow session: after an on-disk edit and
hou.hda.reloadAllFiles() a value written directly to a visualizer is
replaced by the tab's value, and Enable toggles work afterwards.

Co-Authored-By: Claude Fable 5.1 <[email protected]>

 otls/sop_lsgalante.developer_panel.1.0.hdalc | Bin 19389 -> 20381 bytes
 1 file changed, 0 insertions(+), 0 deletions(-)

diff --git a/otls/sop_lsgalante.developer_panel.1.0.hdalc b/otls/sop_lsgalante.developer_panel.1.0.hdalc
index 03f669a..e484371 100755
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