Schedule name required in builder but not enforced in scheduling tool — causes 500

## Bug

In the agent builder, **Schedule Name** is marked as a required field when setting up a scheduled run. However, the scheduling tool does not enforce this as required at submission time.

## Steps to Reproduce

1. Open the scheduling tool
2. Fill out scheduling fields but leave **Schedule Name** blank
3. Submit

## Expected Behavior

Schedule Name should be validated client-side with a clear error before submission.

## Actual Behavior

Form submits successfully but the backend returns a **500 error** because Schedule Name is missing.

## Impact

Poor UX — user gets a silent/confusing 500 with no indication of what went wrong.

## Fix

Add client-side required validation to the Schedule Name field in the scheduling tool, consistent with how it's enforced in the builder.