Crash in text accessibility, UWP (probably WinUI 3 too)

Nobody has claimed this yet.

### Describe the bug

I know this is very vague, but I can't reproduce this issue myself although it accounts for a very large amount of crashes in my app. I can see this stack trace in Partner Center:

```tsv
"Frame" "Image" "Function" "Offset"
"0" "Windows.UI.Xaml.dll" "CInlineCollection::GetRun" "0x0000000000000000"
"1" "Windows.UI.Xaml.dll" "ParagraphTextSource::IsInSurrogateCRLF" "0x0000000000000000"
"2" "Windows.UI.Xaml.dll" "ParagraphTextSource::IsInSurrogateCRLF" "0x0000000000000000"
"3" "Windows.UI.Xaml.dll" "ParagraphNode::IsAtInsertionPosition" "0x0000000000000000"
"4" "Windows.UI.Xaml.dll" "ContainerNode::IsAtInsertionPosition" "0x0000000000000000"
"5" "Windows.UI.Xaml.dll" "RichTextBlockView::IsAtInsertionPosition" "0x0000000000000000"
"6" "Windows.UI.Xaml.dll" "CPlainTextPosition::IsAtInsertionPosition" "0x0000000000000000"
"7" "Windows.UI.Xaml.dll" "CPlainTextPosition::MoveToNextInsertionPosition" "0x0000000000000000"
"8" "Windows.UI.Xaml.dll" "CPlainTextPosition::GetNextInsertionPosition" "0x0000000000000000"
"9" "Windows.UI.Xaml.dll" "CTextRangeAdapter::MoveByCharacter" "0x0000000000000000"
"10" "Windows.UI.Xaml.dll" "CTextRangeAdapter::ExpandToCharacter" "0x0000000000000000"
"11" "Windows.UI.Xaml.dll" "CTextRangeAdapter::MoveEndpointByUnit" "0x0000000000000000"
"12" "Windows.UI.Xaml.dll" "DirectUI::TextRangeAdapter::MoveEndpointByUnitImpl" "0x0000000000000000"
"13" "Windows.UI.Xaml.dll" "DirectUI::TextRangeAdapterGenerated::MoveEndpointByUnit" "0x0000000000000000"
"14" "Windows.UI.Xaml.dll" "DirectUI::AutomationPeer::UIATextRangeInvoke" "0x0000000000000000"
"15" "Windows.UI.Xaml.dll" "CManagedTextRangeProvider::MoveEndpointByUnit" "0x0000000000000000"
"16" "Windows.UI.Xaml.dll" "CUIATextRangeProviderWrapper::MoveEndpointByUnit" "0x0000000000000000"
"17" "UIAutomationCore.DLL" "RemotePatternStub::TextRange_MoveEndpointByUnit" "0x0000000000000000"
"18" "UIAutomationCore.DLL" "InvokePatternMethodOnCorrectContext_Callback" "0x0000000000000000"
```

### Why is this important?

Accounts for 2.5/5% of my app crashes (few millions of active users monthly)

### Steps to reproduce the bug

Can't reproduce unfortunately

### Actual behavior

_No response_

### Expected behavior

_No response_

### Screenshots

_No response_

### NuGet package version

None

### Windows version

_No response_

### Additional context

_No response_

Start with the supplied Windows.UI.Xaml.dll stack trace, especially CInlineCollection::GetRun and the text accessibility path through CTextRangeAdapter::MoveEndpointByUnit. The issue provides no reproduction, Windows version, package version, source file, or test; done would require identifying a reproducible cause and validating a fix against the reported crash path.

Written by the indexing model from the issue text.