Add specs for remaining under-covered form controls

[fpigeonjr]

Parent

#576

What to build

Raise unit-test coverage for the remaining under-covered form controls: sam-sds-autocomplete (69.92%, 251/359 baseline — largest remaining gap at 108 lines), checkbox (53.33%), text (65.33%), select (67.50%), textarea (74.19%), number (74.36%), date-time/sam-form-control (57–60%), radiobutton (95.83%), toggle-switch (90.48%). Combined gap roughly 250 lines.

Acceptance criteria

• Each listed control's line coverage measurably increased from its baseline
• New specs test through each component's public API, not private methods
• All existing and new specs pass under the Vitest runner
• Coverage gate still passes or improves

Blocked by

• Migrate test-app runner from Karma/Jasmine to Vitest (Analog) #626