WrapPanel does not reflow items correctly after window resize

[Chevalier12]

Summary

WrapPanel does not reliably reflow items when the available size changes after initial layout.

Current behavior

• Initial arrangement can appear correct.
• After resizing the host window narrower or wider, wrap breaks are often stale.
• Items may stay on previous rows/positions (or overlap nearby elements) instead of repositioning for the new width.

Expected behavior

• WrapPanel should recompute wrapping immediately whenever available width/height changes.
• Items should reflow to correct rows/positions for both shrink and grow resize paths.

Reproduction

1. Open a view using WrapPanel with multiple buttons/items (for example Frame/Page demo action rows before workaround).
2. Resize the app window significantly narrower, then wider.
3. Observe item placement does not consistently update to new wrap boundaries.

Notes

• Temporary workaround in demos has been to use explicit StackPanel row grouping instead of WrapPanel.
• Root cause likely in measure/arrange interaction where wrap decisions during measure are based on unconstrained width and not invalidated/recomputed on subsequent size changes.