test(frontend): cover ReportTemplatePicker keyboard selection

[utksh1]

Summary

Add component tests for keyboard selection, focus movement, and the selected template callback.

Scope

• Suggested file: frontend/src/components/ReportTemplatePicker.tsx
• Add or extend a focused frontend unit test.
• Do not bundle unrelated visual or production changes.

Acceptance criteria

• The behavior is covered with a deterministic test.
• The user-visible or accessibility outcome is asserted.
• Existing tests remain stable.
• The focused frontend test passes.

Verification

Run the affected Vitest file from frontend/.