[Bug]: Overlay trigger directive content does not get read by screen reader.

### Code of conduct

- [x] I agree to follow this project's code of conduct.

### Impacted component(s)

overlay-trigger-directive

### Library version

1.9.0

### Expected behavior

Overlay content should be read by screen reader when triggered.

### Actual behavior

Overlay content is not read by screen reader when using the trigger directive.

### Screenshots

https://github.com/user-attachments/assets/32dce6db-dd00-4814-aea0-682b92983fb9

### What browsers are you seeing the problem in?

_No response_

### How can we reproduce this issue?

Issue: https://opensource.adobe.com/spectrum-web-components/storybook/index.html?path=/story/overlay-directive--default&globals=system:express

How it should work: https://opensource.adobe.com/spectrum-web-components/storybook/index.html?path=/story/overlay--click-and-hover-target&globals=system:express

### Sample code or abstract reproduction which illustrates the problem

_No response_

### Severity

SEV 2

### Logs taken while reproducing problem

_No response_

### Would you like to track this issue in Jira?

- [x] Yes, please tell me the ticket number!

Start with the overlay-trigger-directive entry point and compare its Storybook reproduction with the overlay--click-and-hover-target example linked in the issue. Verify the trigger's overlay content is exposed to and read by a screen reader when activated, matching the expected behavior.

Written by the indexing model from the issue text.