feat(ui5-toolbar-button): add accessibleDescription property

[plamenivanov91]

Forwards accessibleDescription to the inner ui5-button, enabling aria-describedby support for toolbar actions such as the Go button in the FilterBar header.

Fixes #13591

[github-actions]

👋 Heads-up: dev close is in effect

Thanks for the contribution! This repository is currently in dev close ahead of release 2.26 (scheduled 2026-08-26, UTC). See the release schedule for the full timeline.

This PR appears to introduce public-API changes (detected by diffing the Custom Elements Manifest against the latest published version on npm):

@ui5/webcomponents

• ➕ added property: accessibleDescription
• ➕ added attribute: accessible-description
• 🔄 changed attribute design (type)

Could you please hold off on merging into main until the release ships? Public-API changes are best landed in the next dev cycle so they don't slip into the release at the last minute. Once the release is out, this PR is good to go.

If this change must ship in the current release, please request a review from one or two members of @UI5/ui5-team-webc so the team can sign off explicitly.

💬 False positive? If you believe this PR doesn't actually change the public API (e.g. only internal refactoring, or an entry the detector mis-attributed), please reply on this thread — your feedback helps us improve the detection during this trial run.

Posted automatically by the Dev Close Notice workflow.

[sap-ui5-webcomponents-release]

🚀 Deployed on https://pr-13978--ui5-webcomponents-preview.netlify.app