test sweep: kernel commands + widgets coverage, ratchet floor to 93

Add tests for `keybindings.dart` (KeyEvent → Keybinding mapping,
parse-error edges, resolver entries view), `toolchain_paths.dart`
(the Flutter-free `ToolchainView.resolved` static view), and several
`widgets/src/` primitives: tooltip hover/overlay, palette filter +
submit, multitab controller `copyWith` + size getters, and additional
markdown branches (h3–h6 headings, tables, strikethrough, default
block fallback, record-link tap).

Unfreezes the pre-push coverage floor that was held at 90 on
2026-05-14 by mistake and ratchets to 93. Tidies eight test files
that had accumulated unused imports flagged by `unnecessary_import`.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

test/daemon/dispatcher_test.dart

@@ -2,7 +2,6 @@
 library;
 
 import 'package:clide/clide.dart';
-import 'package:clide/src/daemon/dispatcher.dart';
 import 'package:test/test.dart';
 
 IpcRequest _req(String cmd, {String id = '1', Map<String, Object?> args = const {}}) {

test/daemon/pql_commands_errors_test.dart

@@ -10,7 +10,6 @@ import 'dart:io';
 import 'package:clide/clide.dart';
 import 'package:clide/kernel/src/toolchain_paths.dart';
 import 'package:clide/src/daemon/pql_commands.dart';
-import 'package:clide/src/pql/client.dart';
 import 'package:test/test.dart';
 
 void main() {