fix(editor): a filling code editor starts its text at the top

lib/core/editor/querya_code_editor.dart

@@ -175,6 +175,13 @@ class _QueryaCodeEditorState extends State<QueryaCodeEditor> {
     );
   }
 
+  /// A filling editor starts at the top, like every code editor; an
+  /// explicit [QueryaCodeEditor.textAlignVertical] still wins. (The field's own
+  /// default centres the text of a field that expands.)
+  material.TextAlignVertical? get _verticalAlignment =>
+      widget.textAlignVertical ??
+      (widget.expands ? material.TextAlignVertical.top : null);
+
   Widget? _resolvedPlaceholder() {
     if (widget.placeholder != null) return widget.placeholder;
     return switch (widget.language) {
@@ -202,7 +209,7 @@ class _QueryaCodeEditorState extends State<QueryaCodeEditor> {
         maxLines: widget.expands ? null : widget.maxLines,
         expands: widget.expands,
         style: style,
-        textAlignVertical: widget.textAlignVertical,
+        textAlignVertical: _verticalAlignment,
         decoration: material.InputDecoration(
           border: material.InputBorder.none,
           hintText: widget.hintText,
@@ -221,6 +228,7 @@ class _QueryaCodeEditorState extends State<QueryaCodeEditor> {
       maxLines: widget.expands ? null : widget.maxLines,
       expands: widget.expands,
       style: style,
+      textAlignVertical: _verticalAlignment,
       placeholder: placeholder,
       onChanged: widget.onChanged,
     );

test/core/editor/querya_code_editor_alignment_test.dart

@@ -0,0 +1,68 @@
+import 'package:flutter/material.dart' as material;
+import 'package:flutter/painting.dart' show TextPosition;
+import 'package:flutter_test/flutter_test.dart';
+import 'package:querya_desktop/core/editor/querya_code_editor.dart';
+import 'package:querya_desktop/core/editor/querya_code_language.dart';
+
+import '../../support/querya_theme_test_shell.dart';
+
+void main() {
+  Future<void> pump(
+    WidgetTester tester, {
+    QueryaCodeEditorVariant variant = QueryaCodeEditorVariant.shadcn,
+    material.TextAlignVertical? align,
+  }) async {
+    await tester.pumpWidget(
+      queryaThemeTestShell(
+        child: material.Center(
+          child: material.SizedBox(
+            width: 480,
+            height: 360,
+            child: QueryaCodeEditor(
+              language: QueryaCodeLanguage.plain,
+              variant: variant,
+              enableHighlighting: false,
+              textAlignVertical: align,
+            ),
+          ),
+        ),
+      ),
+    );
+    await tester.pump();
+  }
+
+  Future<double> textOffsetFromTop(WidgetTester tester) async {
+    await tester.enterText(find.byType(material.EditableText), 'select 1');
+    await tester.pump();
+    final field = tester.getRect(find.byType(QueryaCodeEditor));
+    // The widget fills the field either way; the caret shows where the text is.
+    final render = tester
+        .state<material.EditableTextState>(find.byType(material.EditableText))
+        .renderEditable;
+    final caret = render.getLocalRectForCaret(const TextPosition(offset: 0));
+    return render.localToGlobal(caret.topLeft).dy - field.top;
+  }
+
+  testWidgets('the shadcn editor starts its text at the top', (tester) async {
+    await pump(tester);
+
+    expect(await textOffsetFromTop(tester), lessThan(60));
+  });
+
+  testWidgets('the material editor starts its text at the top',
+      (tester) async {
+    await pump(tester, variant: QueryaCodeEditorVariant.material);
+
+    expect(await textOffsetFromTop(tester), lessThan(60));
+  });
+
+  testWidgets('an explicit alignment still wins', (tester) async {
+    await pump(
+      tester,
+      variant: QueryaCodeEditorVariant.material,
+      align: material.TextAlignVertical.center,
+    );
+
+    expect(await textOffsetFromTop(tester), greaterThan(100));
+  });
+}