Don't blank the schema picker while typing a replacement

The previous commit made SchemaLookup emit `select` on every cleared selection.
But CdxLookup also deselects (emits update:selected null) while the user types to
replace an existing value, so editing a set target schema round-tripped an empty
value back and wiped the field mid-edit.

Only emit the clear when the input is actually empty, matching SubjectLookup's
onSubjectSelected guard.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: JeroenDeDauw

resources/ext.neowiki/src/components/common/SchemaLookup.vue

@@ -78,7 +78,11 @@ async function onLookupInput( value: string ): Promise<void> {
 }
 
 function onSchemaSelected( schemaName: string | null ): void {
-	emit( 'select', schemaName ?? '' );
+	if ( schemaName ) {
+		emit( 'select', schemaName );
+	} else if ( !inputText.value ) {
+		emit( 'select', '' );
+	}
 }
 
 function focus(): void {

resources/ext.neowiki/tests/components/common/SchemaLookup.spec.ts

@@ -156,6 +156,16 @@ describe( 'SchemaLookup', () => {
 		expect( wrapper.emitted( 'select' )?.[ 0 ] ).toEqual( [ '' ] );
 	} );
 
+	it( 'does not emit a clear while the user is typing a replacement', () => {
+		const wrapper = mountComponent( { selected: 'Product' } );
+		const lookup = wrapper.findComponent( CdxLookup );
+
+		lookup.vm.$emit( 'update:input-value', 'Off' );
+		lookup.vm.$emit( 'update:selected', null );
+
+		expect( wrapper.emitted( 'select' ) ).toBeFalsy();
+	} );
+
 	it( 'exposes focus method', () => {
 		const CdxLookupStub = {
 			template: '<div><input /></div>',