Add frontend form tests for collaborator percentage totals

[mimijuwonlo-commits]

Area

Frontend split creation

Problem

The frontend should guide users when collaborator shares do not total the required amount. Tests can protect edge cases around decimals and editing.

Acceptance Criteria

• Test under-total, over-total, exact-total, and decimal entry cases
• Show field or form-level feedback
• Prevent submission until totals are valid
• Preserve accessible error messaging

Validation

Run CreateSplitWizard validation tests.