add Toolchain, GitClient, native directory picker

Toolchain centralizes binary resolution — replaces five ad-hoc
mechanisms (expandedPath, _resolveGit, _resolve, _resolvePtyc,
_existsOnPath). Resolves via Future.delayed after runApp to avoid
blocking the merged UI/platform thread on macOS.

GitClient wraps all git operations with a typed API. Every subprocess
call goes through _run() using toolchain.git + toolchain.gitEnv.
Replaces free functions in operations.dart.

Native directory picker: NSOpenPanel on macOS (method channel in
AppDelegate), GtkFileChooserDialog on Linux. Falls back to text-input
dialog on web or MissingPluginException. Shows "No git repo found"
dialog when the selected directory is not a git repository.

PqlClient and pane commands updated to use Toolchain. ToolCheck
replaced by Toolchain.missing/allOk. All IPC handlers now catch
GitException to prevent unhandled exceptions on the merged thread.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

lib/kernel/src/facade.dart

@@ -27,7 +27,7 @@ import 'package:clide/kernel/src/secrets.dart';
 import 'package:clide/kernel/src/settings.dart';
 import 'package:clide/kernel/src/theme/controller.dart';
 import 'package:clide/kernel/src/theme/loader.dart';
-import 'package:clide/kernel/src/tool_check.dart';
+import 'package:clide/kernel/src/toolchain.dart';
 import 'package:clide/kernel/src/tray.dart';
 import 'package:clide/kernel/src/window_controls.dart';
 import 'package:flutter/widgets.dart';
@@ -61,7 +61,7 @@ class KernelServices {
     required this.project,
     required this.extensions,
     required this.window,
-    required this.toolCheck,
+    required this.toolchain,
     required this.scheduler,
   });
 
@@ -89,7 +89,7 @@ class KernelServices {
   final ProjectManager project;
   final ExtensionManager extensions;
   final WindowControls window;
-  final ToolCheck toolCheck;
+  final Toolchain toolchain;
   final SchedulerService scheduler;
 
   static Future<KernelServices> boot({
@@ -103,6 +103,7 @@ class KernelServices {
     String? socketPath,
     DaemonClient Function(Logger, DaemonBus)? daemonClientFactory,
     bool autoStartDaemonClient = true,
+    Toolchain? toolchain,
   }) async {
     final log = Logger();
     final events = DaemonBus();
@@ -138,13 +139,14 @@ class KernelServices {
     final net = NetworkStatus();
     final focus = FocusTracker();
     final window = WindowControls();
-    final toolCheck = ToolCheck();
+    final tc = toolchain ?? Toolchain();
     final scheduler = SchedulerService(events);
     scheduler.start();
     final project = ProjectManager(
       log: log,
       events: events,
       settings: settings,
+      toolchain: tc,
     );
     final ipc = daemonClientFactory != null
         ? daemonClientFactory(log, events)
@@ -207,7 +209,7 @@ class KernelServices {
       project: project,
       extensions: extensions,
       window: window,
-      toolCheck: toolCheck,
+      toolchain: tc,
       scheduler: scheduler,
     );
   }

lib/kernel/src/project.dart

@@ -5,6 +5,7 @@ import 'package:clide/kernel/src/events/bus.dart';
 import 'package:clide/kernel/src/events/types.dart';
 import 'package:clide/kernel/src/log.dart';
 import 'package:clide/kernel/src/settings.dart';
+import 'package:clide/kernel/src/toolchain.dart';
 import 'package:flutter/foundation.dart';
 
 class RecentProject {
@@ -47,13 +48,16 @@ class ProjectManager extends ChangeNotifier {
     required Logger log,
     required DaemonBus events,
     required SettingsStore settings,
+    required Toolchain toolchain,
   })  : _log = log,
         _events = events,
-        _settings = settings;
+        _settings = settings,
+        _toolchain = toolchain;
 
   final Logger _log;
   final DaemonBus _events;
   final SettingsStore _settings;
+  final Toolchain _toolchain;
 
   Directory? _current;
   Directory? get current => _current;
@@ -116,7 +120,7 @@ class ProjectManager extends ChangeNotifier {
 
   Future<String?> resolveWorkspace(String path) async {
     try {
-      final r = await Process.run('git', ['rev-parse', '--show-toplevel'], workingDirectory: path, runInShell: false);
+      final r = await Process.run(_toolchain.git, ['rev-parse', '--show-toplevel'], workingDirectory: path, environment: _toolchain.gitEnv);
       if (r.exitCode != 0) return null;
       final out = (r.stdout as String).trim();
       return out.isEmpty ? null : out;
@@ -128,7 +132,7 @@ class ProjectManager extends ChangeNotifier {
 
   Future<String?> _currentBranch(String root) async {
     try {
-      final r = await Process.run('git', ['rev-parse', '--abbrev-ref', 'HEAD'], workingDirectory: root, runInShell: false);
+      final r = await Process.run(_toolchain.git, ['rev-parse', '--abbrev-ref', 'HEAD'], workingDirectory: root, environment: _toolchain.gitEnv);
       if (r.exitCode != 0) return null;
       final out = (r.stdout as String).trim();
       return out.isEmpty ? null : out;

lib/kernel/src/tool_check.dart

@@ -2,6 +2,8 @@ import 'dart:io';
 
 import 'package:flutter/foundation.dart';
 
+import '../../src/pty/env.dart';
+
 class ToolCheck extends ChangeNotifier {
   bool ptycOk = false;
   bool pqlOk = false;
@@ -18,24 +20,31 @@ class ToolCheck extends ChangeNotifier {
         if (!gitOk) 'git not found',
       ];
 
+  /// Workspace root, set by the app at boot. Falls back to cwd.
+  static String? workspaceRoot;
+
   Future<void> check() async {
-    final cwd = Directory.current.path;
-    ptycOk = File('$cwd/native/linux-x64/ptyc').existsSync() ||
-        File('$cwd/ptyc/bin/ptyc').existsSync() ||
-        await _which('ptyc');
-    pqlOk = await _which('pql');
-    tmuxOk = await _which('tmux');
-    gitOk = await _which('git');
+    final root = workspaceRoot ?? Directory.current.path;
+    ptycOk = File('$root/native/linux-x64/ptyc').existsSync() ||
+        File('$root/native/macos-arm64/ptyc').existsSync() ||
+        File('$root/native/macos-x64/ptyc').existsSync() ||
+        File('$root/ptyc/bin/ptyc').existsSync() ||
+        _existsOnPath('ptyc');
+    pqlOk = _existsOnPath('pql');
+    tmuxOk = _existsOnPath('tmux');
+    gitOk = _existsOnPath('git');
     checked = true;
     notifyListeners();
   }
 
-  static Future<bool> _which(String name) async {
-    try {
-      final r = await Process.run('which', [name]);
-      return r.exitCode == 0;
-    } catch (_) {
-      return false;
+  /// Check if [name] exists as an executable in any PATH directory.
+  /// Uses direct file-existence checks — works inside a macOS sandbox
+  /// without needing to exec `which`.
+  static bool _existsOnPath(String name) {
+    for (final dir in expandedPath.split(':')) {
+      if (dir.isEmpty) continue;
+      if (File('$dir/$name').existsSync()) return true;
     }
+    return false;
   }
 }

lib/kernel/src/toolchain.dart

@@ -0,0 +1,146 @@
+/// Centralized binary resolution for external tools.
+///
+/// Resolution runs in a background isolate via [resolvePaths] to avoid
+/// blocking the merged UI/platform thread on macOS. The result is
+/// applied on the main thread via [applyResolved].
+library;
+
+import 'dart:async';
+import 'dart:io';
+
+import 'package:flutter/foundation.dart';
+
+import '../../src/pty/env.dart' show expandedPath;
+
+/// Serializable result of tool resolution (crosses isolate boundary).
+class ResolvedPaths {
+  const ResolvedPaths({
+    this.git,
+    this.pql,
+    this.tmux,
+    this.ptyc,
+    this.shell,
+    this.gitEnv,
+  });
+
+  final String? git;
+  final String? pql;
+  final String? tmux;
+  final String? ptyc;
+  final String? shell;
+  final Map<String, String>? gitEnv;
+}
+
+class Toolchain extends ChangeNotifier {
+  String? _git;
+  String? _pql;
+  String? _tmux;
+  String? _ptyc;
+  String? _shell;
+  Map<String, String>? _gitEnv;
+  bool _resolved = false;
+
+  String get git => _git ?? 'git';
+  String get pql => _pql ?? 'pql';
+  String get tmux => _tmux ?? 'tmux';
+  String get ptyc => _ptyc ?? 'ptyc';
+  String get shell => _shell ?? '/bin/bash';
+
+  /// Extra environment variables for git (e.g. GIT_EXEC_PATH for dugite).
+  Map<String, String>? get gitEnv => _gitEnv;
+
+  bool get resolved => _resolved;
+  bool get allOk => _resolved && missing.isEmpty;
+
+  List<String> get missing => [
+        if (_git == null) 'git',
+        if (_pql == null) 'pql',
+        if (_tmux == null) 'tmux',
+        if (_ptyc == null) 'ptyc',
+      ];
+
+  /// Returns a Future that completes when resolution finishes.
+  Future<void> waitForResolution() {
+    if (_resolved) return Future.value();
+    final c = Completer<void>();
+    void listener() {
+      if (_resolved) {
+        removeListener(listener);
+        if (!c.isCompleted) c.complete();
+      }
+    }
+    addListener(listener);
+    return c.future;
+  }
+
+  /// Apply paths resolved in a background isolate.
+  void applyResolved(ResolvedPaths p) {
+    _git = p.git;
+    _pql = p.pql;
+    _tmux = p.tmux;
+    _ptyc = p.ptyc;
+    _shell = p.shell;
+    _gitEnv = p.gitEnv;
+    _resolved = true;
+    notifyListeners();
+  }
+
+  /// Pure function — runs in a background isolate. All file I/O happens
+  /// here, off the main thread.
+  static ResolvedPaths resolvePaths({required String workspaceRoot}) {
+    final dugite = '$workspaceRoot/native/dugite/bin';
+
+    String? git;
+    Map<String, String>? gitEnv;
+    final dugiteGit = _firstExisting(['$dugite/git']);
+    if (dugiteGit != null) {
+      git = dugiteGit;
+      final dugiteRoot = File(dugiteGit).parent.parent.path;
+      gitEnv = {
+        'GIT_EXEC_PATH': '$dugiteRoot/libexec/git-core',
+        'GIT_TEMPLATE_DIR': '$dugiteRoot/share/git-core/templates',
+      };
+    } else {
+      git = _findOnPath('git');
+    }
+
+    final pql = _findOnPath('pql');
+    final tmux = _findOnPath('tmux');
+    final shell = _findOnPath(
+        Platform.environment['SHELL']?.split('/').last ?? 'bash');
+
+    final ptyc = _firstExisting([
+      '$workspaceRoot/ptyc/bin/ptyc',
+      '$workspaceRoot/native/linux-x64/ptyc',
+      '$workspaceRoot/native/macos-arm64/ptyc',
+      '$workspaceRoot/native/macos-x64/ptyc',
+      if (Platform.environment['HOME'] case final home?)
+        '$home/.local/bin/ptyc',
+    ]) ?? _findOnPath('ptyc');
+
+    return ResolvedPaths(
+      git: git,
+      pql: pql,
+      tmux: tmux,
+      ptyc: ptyc,
+      shell: shell,
+      gitEnv: gitEnv,
+    );
+  }
+
+  static String? _findOnPath(String name) {
+    for (final dir in expandedPath.split(':')) {
+      if (dir.isEmpty) continue;
+      final f = File('$dir/$name');
+      if (f.existsSync()) return f.path;
+    }
+    return null;
+  }
+
+  static String? _firstExisting(List<String> candidates) {
+    for (final c in candidates) {
+      if (File(c).existsSync()) return c;
+    }
+    return null;
+  }
+}

lib/kernel/src/window_controls.dart

@@ -65,4 +65,12 @@ class WindowControls extends ChangeNotifier {
       return false;
     }
   }
+
+  /// Opens the native OS directory picker.
+  /// Returns the selected path, or null if the user cancelled.
+  /// Throws [MissingPluginException] if the platform has no handler,
+  /// so callers can fall back to a text-input dialog.
+  Future<String?> pickDirectory() {
+    return _channel.invokeMethod<String>('pickDirectory');
+  }
 }