Characters at the beginning and the end of a math expression are not spoken when navigating character by character in Word 365

eDAD tracking ticket for this issue is [Accessibility 228598](https://dev.azure.com/CSS-IRT/CSS%20IRT/_workitems/edit/228598)

## Description:
There are issues of content not being spoken when using the left/right arrow keys to navigate character by character in and out of a math expression:
- The character immediately following an expression is not spoken when navigating character-by-character in either direction
- The first character of an expression is not spoken when navigating character-by-character into the expression (going right)

## Steps to Reproduce:
1. Launch the JAWS screen reader
2. Configure JAWS:
a. Enable MathCAT
b. Configure MathCAT
1. Speech Style: ClearSpeak
2. Math Verbosity: Verbose
c. Restart JAWS if changes were made
6. Open the attached file ([Text before and after math expression.docx](https://github.com/user-attachments/files/16456183/Text.before.and.after.math.expression.docx)) with Microsoft Word 365 (Desktop version)
6. Navigate to the line with the math expression
7. Use the left and right arrow keys to move character-by-character in and out of the start and end of the expression
8. Observe that:
a. Not all keypresses result in audio being produced
b. The first character of the expression is not spoken when navigating into the expression from the left.
c. The first character of text after the expression will not be spoken when navigating past it from either direction

## Expected Behavior:
When navigating character by character with a screen reader, each press of the left or right arrow keys should result in some audio being produced. Also, text characters and other content should be reliably spoken when navigating over it.

## Observed Behavior:
Not all left-arrow or right-arrow keypresses result in audio being produced. Some content that is present in the document is not spoken when navigating over it character-by-character.

## Version Information:
- **OS Version:**
-- OS Name: Microsoft Windows 11 Enterprise
-- Version: 10.0.22621 Build 22621
-- Locale: United States
- **Microsoft Word Version:**
-- Microsoft 365 Apps for enterprise
-- Version 2402 (Build 17328.20452 Click-to-Run)
- **JAWS Version and Settings**
-- JAWS Professional Version 2024.2406.121
-- Configured to use MathCAT with ClearSpeak Verbose

## Example Video and Sample Document:
I have provided a link to a short example video demonstrating the issue, and attached the Word document used in the video.

### Attachments:
- [Video: Characters at the beginning/end of expressions disappear when navigating character by character in and out of a math expression in Word 365 (7 minutes)](https://iu.mediaspace.kaltura.com/media/t/1_rgxfq1o5)
- [Text before and after math expression.docx](https://github.com/user-attachments/files/16456183/Text.before.and.after.math.expression.docx)