Fix capture grid dismissed by map popup light-dismiss

[emosaru]

Summary

• Fixes Capturing items no longer work, cancels out of menu #42 — clicking items in the capture grid popup was closing the location details popup before the capture could register
• The tunneling PointerPressed handler now detects clicks inside child popups (capture grid, etc.) by checking whether the visual root is the TopLevel window; popup overlays have a different root and are left alone

Root cause

Popup content in Avalonia renders on an overlay layer with a disconnected visual tree. The light-dismiss handler walked up from e.Source looking for LocationDetailsContent, but for nested popups (capture grid inside location details), the walk terminates at the overlay host without ever reaching LocationDetailsContent. The handler incorrectly treated this as an "outside" click.

Test plan

• Open a map location popup, click a section's capture icon → capture grid opens
• Click an item in the capture grid → item should be captured, popup closes normally
• Click "Clear" in the capture grid → captured item should be cleared
• Click outside both popups (on a tracker item, empty space, etc.) → location details popup should close
• Double-click a map location → should still pin correctly

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