[ci-scan] Recurring Android CollectionView header and footer UI test timeouts

## Summary
The Android CollectionView header/footer feature fixture repeatedly times out after its first failure, affecting item-layout and item-source variants in two of the last ten main builds.

## Build Information
- **Pipeline**: maui-pr-uitests
- **Build**: https://dev.azure.com/dnceng-public/public/_build/results?buildId=1574142
- **Build ID**: 1574142
- **Branch**: main
- **First seen**: 2026-08-24
- **Occurrences**: 2 in last 10 builds

## Affected Legs
- Android UI tests / Android emulator
- CollectionView header/footer item-layout and item-source cases

## Error Message
```
2026-08-30T14:26:52.6890957Z Failed VerifyHeaderViewWithItemsLayoutHorizontalGrid [15 s]
```

The same run subsequently failed the horizontal-list, vertical-grid, no-items-source, and observable-collection header variants with the same element wait timeout pattern.

## Recommended Action
Investigate fixture state and element discovery in the Android CollectionView header/footer feature tests, starting with `VerifyHeaderViewWithItemsLayoutHorizontalGrid`; prevent one timed-out case from leaving stale state that causes the remaining variants to cascade.

Start with the Android UI test fixture and the named VerifyHeaderViewWithItemsLayoutHorizontalGrid case, using build 1574142 and its failure log to reproduce the timeout. Trace fixture state and element discovery across the listed header and footer variants. Done means the initial timeout no longer leaves stale state and the remaining variants do not cascade into element wait failures.

Written by the indexing model from the issue text.