fix(client/windows): settings combos render blank until touched

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>

clients/windows/src/app/settings.rs

@@ -690,11 +690,17 @@ pub(crate) fn settings_page(
     )
     .chain(groups)
     .collect();
+    // The keyed column MUST sit inside a panel's child list, not directly under the
+    // scroll_view: `ScrollView::children()` is `Children::PositionalSingle`, which
+    // reconciles its one child POSITIONALLY and ignores keys outright. Keyed straight onto
+    // the scroll_view's child, the section switch silently diffs one section's controls into
+    // another's — which re-sets each reused ComboBox's items (clearing WinUI's selection)
+    // but skips `selected_index` whenever the two sections' values compare equal, so the
+    // combos render blank until touched. A panel (vstack) takes the keyed path, so the key
+    // remounts the whole column and every prop is applied fresh.
     let content = scroll_view(
-        vstack(titled)
-            .spacing(10.0)
-            .margin(edges(24.0, 20.0, 28.0, 40.0))
-            .with_key(section),
+        vstack(vec![vstack(titled).spacing(10.0).with_key(section).into()])
+            .margin(edges(24.0, 20.0, 28.0, 40.0)),
     )
     .opacity(progress)
     .margin(edges(0.0, (1.0 - progress) * 22.0, 0.0, 0.0));