fix(a11y)-3: prevent rendering empty dialog title headings

[Sagar-6203620715]

Summary

This PR fixes accessibility violations by preventing DialogTitle from rendering empty heading elements when no title content is provided.

Related Issue

• WIP: Accessibility Issues Tracking #4385

Addresses point 3 from the accessibility issue

Changes

• Updated DialogTitle to return null when both children and action buttons are absent
• Conditionally render the heading only when title content exists
• Preserved rendering of dialog action buttons when present

Steps to Test

1. Open Storybook and navigate to dialogs without a title
2. Run accessibility checks (Axe)
3. Verify no empty heading violations are reported

Screenshots (if applicable)

N/A

Notes for the Reviewer

• Centralized fix in Dialog.tsx; no story files were modified
• Maintains existing dialog behavior while improving accessibility

[Copilot]

Pull request overview

This PR fixes accessibility violations by preventing the DialogTitle component from rendering empty <h1> heading elements when no title content is provided. This addresses 11 empty heading violations identified by axe-storybook-testing across various dialog components (AuthToken, AuthChooser, and Chooser stories).

Changes:

• Added early return in DialogTitle when both children and action buttons are absent to avoid rendering the component entirely
• Conditionally render the title content Grid item only when children exist to prevent empty <h1> elements
• Preserved rendering of dialog action buttons when present, ensuring fullscreen and close buttons still appear

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[illume]

🎉 thanks!

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: illume, Sagar-6203620715

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