fix: remove default column selection in ColumnSelector

[Creylay]

Fix: Remove Default Column Selection in ColumnSelector

Summary

This PR removes the automatic column selection behavior in the ColumnSelector component used during the explorer creation workflow.
Now, no columns are selected by default — users must manually select them.

Changes

ColumnSelector.jsx

• Updated logic to prevent automatic selection of valid columns.
• Ensures initial selection state is always empty ([]).
• Maintains all existing cardinality validation (min, max, exact).

ScopeStepConverter.jsx

• Added: State isColumnSelectionValid for tracking column validation.
• Connected: Callback onValidationChange to propagate validation state.
• Improved: Button logic now includes column validation before proceeding.

Result

• No columns are pre-selected when the step loads.
• User must select columns manually.
• Cardinality validation (min, max, exact) still applies.
• Button “Next/Save” remains disabled until selection is valid.

Testing Steps

1. Open the explorer creation workflow.
2. Go to Step 1: Select Scope.
3. Confirm that no columns are selected initially.
4. Verify that the button “Next” is disabled until valid selection.

Type of Change

• Bug fix (non-breaking change)