chore: clean analyzer to zero issues

Whole-project `flutter analyze` exited 1 on 17 pre-existing info/warning
lints (no errors) in dev tools and test files. Clean them so analyze is
green:
- editor_repository_test: drop the redundant sqflite_common import; keep
  the used utils import with a transitive-dep ignore.
- pen_* widget tests: `(_, __)` wildcard params -> `(_, _)`.
- search_snippet_test / gen_bench_pdf / gen_dense_strokes: drop needless
  interpolation braces; remove an unused `Size` show and an unused local;
  mark the gen tool as print-allowed.

No runtime behavior changed. flutter analyze: No issues found. Affected
tests: 22/22 pass.

test/editor_repository_test.dart

@@ -9,8 +9,7 @@ import 'dart:io';
 
 import 'package:flutter_test/flutter_test.dart';
 import 'package:path/path.dart' as p;
-import 'package:sqflite_common/sqlite_api.dart';
-import 'package:sqflite_common/utils/utils.dart' as sqflite_utils;
+import 'package:sqflite_common/utils/utils.dart' as sqflite_utils; // ignore: depend_on_referenced_packages
 import 'package:sqflite_common_ffi/sqflite_ffi.dart';
 
 import 'package:badnote/editor/engine/stroke_model.dart';

test/pen_canvas_widget_test.dart

@@ -36,7 +36,7 @@ void main() {
               strokeWidth: 0.004,
               allowFingerDrawing: allowFinger,
               onStrokeComplete: onComplete,
-              onEraseStroke: (_, __) {},
+              onEraseStroke: (_, _) {},
             ),
           ),
         ),

test/pen_coordinate_widget_test.dart

@@ -34,7 +34,7 @@ void main() {
               color: const Color(0xFF000000),
               strokeWidth: 0.004,
               onStrokeComplete: committed.add,
-              onEraseStroke: (_, __) {},
+              onEraseStroke: (_, _) {},
             ),
           ),
         ),

test/pen_tool_widget_test.dart

@@ -34,7 +34,7 @@ void main() {
                 strokeWidth: 0.02,
                 allowFingerDrawing: allowFinger,
                 onStrokeComplete: onComplete,
-                onEraseStroke: (_, __) {},
+                onEraseStroke: (_, _) {},
               ),
             ),
           ),

test/pen_zoom_widget_test.dart

@@ -29,7 +29,7 @@ void main() {
                 color: const Color(0xFF000000),
                 strokeWidth: 0.004,
                 onStrokeComplete: (_) {},
-                onEraseStroke: (_, __) {},
+                onEraseStroke: (_, _) {},
               ),
             ),
           ),

test/search_snippet_test.dart

@@ -53,7 +53,7 @@ void main() {
 
   test('the full match is included even when longer than the window', () {
     final long = 'x' * 100;
-    final s = snippetFor('pre ${long} post', long, window: 10)!;
+    final s = snippetFor('pre $long post', long, window: 10)!;
     expect(s.match, long);
     expect(s.matchLength, 100);
   });

tool/gen_bench_pdf.dart

@@ -27,7 +27,7 @@
 
 import 'dart:io';
 import 'dart:math';
-import 'dart:ui' show Offset, Rect, Size;
+import 'dart:ui' show Offset, Rect;
 
 import 'package:flutter_test/flutter_test.dart';
 import 'package:syncfusion_flutter_pdf/pdf.dart';
@@ -207,7 +207,7 @@ void main() {
     final sizeKb = (outFile.lengthSync() / 1024).toStringAsFixed(1);
     print('Generated: $outputPath');
     print('Pages: $pageCount');
-    print('Size: ${sizeKb} KB (${outFile.lengthSync()} bytes)');
+    print('Size: $sizeKb KB (${outFile.lengthSync()} bytes)');
 
     expect(outFile.existsSync(), isTrue);
     expect(outFile.lengthSync(), greaterThan(1024),

tool/gen_dense_strokes.dart

@@ -1,3 +1,4 @@
+// ignore_for_file: avoid_print
 // tool/gen_dense_strokes.dart
 //
 // Generates synthetic ink-stroke datasets as JSON matching InkStroke.toJson()
@@ -52,7 +53,7 @@ void main(List<String> args) {
 
   final sizeKb = (File(outputPath).lengthSync() / 1024).toStringAsFixed(1);
   print('Output: $outputPath');
-  print('Size: ${sizeKb} KB');
+  print('Size: $sizeKb KB');
   for (final count in counts) {
     print('  "$count": ${(result[count.toString()] as List).length} strokes');
   }
@@ -183,15 +184,6 @@ void _verifyRoundTrip(dynamic dataset) {
   final encoded = jsonEncode(raw);
   final decoded = jsonDecode(encoded) as Map<String, dynamic>;
 
-  // Assert required InkStroke fields exist with correct types.
-  void check(String field, Type type) {
-    final val = decoded[field];
-    assert(
-      val == null || val.runtimeType.toString().contains(type.toString()) || val is num || val is String || val is bool || val is List,
-      'Field "$field" missing or wrong type: ${val.runtimeType}',
-    );
-  }
-
   assert(decoded['id'] is String, 'id must be String');
   assert(decoded['points'] is List, 'points must be List');
   assert(decoded['tool'] == 'pen', 'tool enum must be "pen"');