fix(overlay): Overlay trigger directive content not announced by screen readers

[Rajdeepc]

Description

When using the trigger() directive (e.g., ${trigger(popover)}), overlay content was not being announced by screen readers. The ClickController was missing the prepareDescription()method that establishes the ARIA relationship between the trigger and overlay content, unlikeHoverControllerandLongpressController` which already had this functionality.

Solution

1. Added prepareDescription() to ClickController
   Implemented the missing method following the same pattern as HoverController:

   • Determines the appropriate ARIA strategy based on DOM tree relationships
   • Sets aria-describedby on the trigger to reference overlay content
   • Provides proper cleanup via releaseDescription()

2. Made prepareDescription() idempotent
   Added guards to prevent duplicate calls:

override releaseDescription = noop;

override prepareDescription(): void {
    // Do not reapply until target is recycled
    if (this.releaseDescription !== noop) return;
    // ... rest of implementation
}

3. Added observeOverlayElements() in InteractionController
   Handles async content loading:

   • Waits for overlay.updateComplete
   • Calls prepareDescription() when elements are ready
   • Ensures aria-describedby is set even when content loads after the overlay is created

4. Improved trigger change handling in Overlay.willUpdate()
   When the trigger element changes:

   • Releases description from the old trigger
   • Binds new events
   • Prepares description for the new trigger (if elements are already present)

Motivation and context

Before: Click-triggered overlays were not announced by screen readers
After: All trigger types (click, hover, longpress) properly announce overlay content via aria-describedby

Related issue(s)

• fixes [Issue Number]

Screenshots (if appropriate)

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Author's checklist

• I have read the CONTRIBUTING and PULL_REQUESTS documents.
• I have reviewed at the Accessibility Practices for this feature, see: Aria Practices
• I have added automated tests to cover my changes.
• I have included a well-written changeset if my change needs to be published.
• I have included updated documentation if my change required it.

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• Validated on all supported browsers
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Pull Request Test Coverage Report for Build 18528411984

Details

• 118 of 118 (100.0%) changed or added relevant lines in 4 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.007%) to 97.964%

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Totals
Change from base Build 18509542516:	0.007%
Covered Lines:	34299
Relevant Lines:	34833

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