The section-switch key was moved onto the scroll_view's direct child during
the parity restructure, which silently disabled it: ScrollView::children()
is Children::PositionalSingle, reconciled positionally with keys ignored.
The column was therefore reused across section switches, diffing one
section's controls into another's -- which re-sets a reused ComboBox's items
(clearing WinUI's selection) but skips selected_index whenever the two
sections' values compare equal, so every combo rendered empty until changed.
Put the keyed column back inside a panel's child list, where the keyed diff
path actually runs and the switch remounts. This is the same bug the
original code carried a comment about; the comment now names the
PositionalSingle trap that makes the key placement load-bearing.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
enricobuehler
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