[Bug]: XAML formatting inserts a line break between adjacent inline elements and changes the rendered text #1912

Description

First of all, thank you very much for creating CSharpier!
I love it because it ends all styling/formatting wars, so it stops teams wasting value time on this topic which is better spend on other things.

When two inline elements (e.g. in a TextBlock) follow each other directly, without any whitespace between them, CSharpier puts each of them on its own line. In XAML this is not a pure formatting change. The inserted line break is rendered as a space, so
the text shown on screen changes.

The problem occurs with xmlWhitespaceSensitivity set to ignore and also with it set to strict. There is currently no setting that avoids it.

This affects both WPF (.xaml) and Avalonia (.axaml) files in my project.

Steps to Reproduce

1. Use the following configuration in .csharpierrc.json:

   {
     "xmlWhitespaceSensitivity": "strict"
   }

The result is the same with "ignore".

2. Create a XAML file with this content:

   <TextBlock>
       <Run>Sub</Run><Run>total</Run>
   </TextBlock>

3. Format the file with CSharpier.

Environment:

• CSharpier version: 1.3.0
• Run through: CLI and Rider plugin
• Operating system: Windows 11

Expected Behavior

The two Run elements stay on the same line, because there is no whitespace between them in the source file:

<TextBlock>
    <Run>Sub</Run><Run>total</Run>
</TextBlock>

The rendered text stays Subtotal.

Actual Behavior

CSharpier moves the second Run element to a new line:

<TextBlock>
    <Run>Sub</Run>
    <Run>total</Run>
</TextBlock>

The rendered text is now Sub total instead of Subtotal, so the formatting changed the visible output of the application.

The reason is that TextBlock.Inlines is an InlineCollection. That class is marked with WhitespaceSignificantCollectionAttribute, which tells the XAML parser to treat whitespace inside the collection as significant. A line break between two inline elements is normalized into a single space and is really
rendered. See "White-space processing in XAML", section "White space and text content models in WPF":
https://learn.microsoft.com/en-us/dotnet/desktop/xaml-services/white-space-processing

So for elements inside such a collection the following rule has to hold, independent of the xmlWhitespaceSensitivity setting: if there was no whitespace between two elements in the source, none may be inserted.

I expect the same problem for other inline elements in the same position, for example Bold, Italic, Span and Hyperlink, and for mixed content like <TextBlock>Sub<Run>total</Run></TextBlock>.

As a workaround, a <!-- csharpier-ignore --> comment before the affected element keeps the formatting intact. That works, but it is not practical when many views contain such text, and it is easy to forget when writing new XAML.