test(draw): cover the 2.9.0 drawing-card additions to clear the coverage floor

The drawing-card feature batch (icon/image/compare/graph/d2 cards, --stdin,
tool resolution) added widget + wiring code that dipped total coverage under
the 95% floor — surfaced by `make release` (push-check skips coverage). Cover
the gaps: ProblemsController.refresh, every SVG shape-type bbox + the style
vocabulary, _spawnD2 via a real /bin/cat, the icon-show bus path + error
branches, and quad/arc/close marker paths.

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

test/builtin/tools_settings/extension_test.dart

@@ -44,4 +44,17 @@ void main() {
     expect(f.services.settings.get<bool>('app.tools.detected'), isTrue);
     expect(activeSupporterBinaries, isNotNull);
   });
+
+  test('exposes its id, title, and version', () {
+    final ext = ToolsSettingsExtension();
+    expect(ext.id, 'builtin.tools-settings');
+    expect(ext.title, isNotEmpty);
+    expect(ext.version, isNotEmpty);
+  });
+
+  test('deactivate removes the live-sync listener', () async {
+    await f.services.extensions.deactivate('builtin.tools-settings');
+    // Listener gone — a settings write no longer rebuilds the resolver, no throw.
+    await f.services.settings.set<String>(supporterToolKey('d2'), '/x/d2');
+  });
 }