fix(ui5-shellbar): acc findings fixed

[PetyaMarkovaBogdanova]

5) ShellBar (9 failing)

• Repeated continuum ARIA validity violations:
• Rule 281: aria-expanded not allowed on the flagged button host in these rendered cases.
• Rule 270: aria-required not allowed on the flagged switch host.
• Rule 736: dialog section without computable accessible name (missing dialog naming mechanism).
• Impacted tests include search-field scenarios, responsive/overflow behavior, and keyboard navigation checks.

ShellBar	aria-expanded invalid on flagged host	Rule 281	aria-expanded applied to element/role that does not support it in rendered state	Mixed, host-role dependent	Medium	Apply aria-expanded only to actual disclosure control element and only when relationship exists	Control with aria-expanded is the one toggling popup/menu and has proper controls linkage
ShellBar	aria-required invalid on switch host	Rule 270	aria-required set on role that does not support it (or wrong element in composed control)	Mixed, role mapping dependent	Medium	Remove unsupported aria-required or place on valid form role element only	No unsupported aria-required on switch-like hosts
ShellBar	Dialog section without accessible name	Rule 736	Dialog/popup region lacks aria-label or aria-labelledby to visible title	Likely real	High	Ensure every dialog variant has deterministic naming source	Dialog name is computable in search, overflow, and keyboard-opened states

[ui5-webcomponents-bot]

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