feat: custom native file picker showing hidden files/folders

Replaced file_picker's Load/Browse with a custom NativePickerRegistrar
Swift plugin that opens NSOpenPanel with showsHiddenFiles = true.
The file_picker package hardcodes this to false, making hidden folders
like ~/.claude invisible in its dialogs.

Changes:
- New NativePickerRegistrar.swift: custom NSOpenPanel with hidden files
- New NativePicker Dart service using method channel
- Browse: only shows folders (canChooseFiles=false), hidden visible
- Load: only shows .jsonl files, hidden folders visible
- Registered via AppDelegate.applicationDidFinishLaunching
- Removed file_picker dependency from home_screen imports
- Fixed all info-level lint issues (super params, null-aware, doc comment)
- Signed, notarized, stapled DMG

lib/models/content_block.dart

@@ -22,8 +22,8 @@ class ContentBlock {
 class TextBlock extends ContentBlock {
   final String text;
 
-  TextBlock({required this.text, required Map<String, dynamic> raw})
-      : super(type: 'text', raw: raw);
+  TextBlock({required this.text, required super.raw})
+      : super(type: 'text');
 
   factory TextBlock.fromJson(Map<String, dynamic> json) {
     return TextBlock(
@@ -40,8 +40,8 @@ class ThinkingBlock extends ContentBlock {
   ThinkingBlock({
     required this.thinking,
     this.signature,
-    required Map<String, dynamic> raw,
-  }) : super(type: 'thinking', raw: raw);
+    required super.raw,
+  }) : super(type: 'thinking');
 
   factory ThinkingBlock.fromJson(Map<String, dynamic> json) {
     return ThinkingBlock(
@@ -63,8 +63,8 @@ class ToolUseBlock extends ContentBlock {
     required this.name,
     required this.input,
     this.linkedResult,
-    required Map<String, dynamic> raw,
-  }) : super(type: 'tool_use', raw: raw);
+    required super.raw,
+  }) : super(type: 'tool_use');
 
   factory ToolUseBlock.fromJson(Map<String, dynamic> json) {
     return ToolUseBlock(

lib/screens/home/home_screen.dart

@@ -1,8 +1,8 @@
 import 'dart:io';
-import 'package:file_picker/file_picker.dart';
 import 'package:flutter/material.dart';
 import 'package:provider/provider.dart';
 import '../../providers/session_provider.dart';
+import '../../services/native_picker.dart';
 import '../../theme/app_theme.dart';
 
 // ─── Data models ─────────────────────────────────────────────
@@ -120,7 +120,7 @@ class _HomeScreenState extends State<HomeScreen> {
   }
 
   /// Returns the real user home directory, even inside App Sandbox.
-  /// In sandbox, HOME points to ~/Library/Containers/<bundleid>/Data.
+  /// In sandbox, HOME points to `~/Library/Containers/bundleid/Data`.
   String? _getRealHome() {
     final home = Platform.environment['HOME'];
     if (home == null) return null;
@@ -333,8 +333,9 @@ class _HomeScreenState extends State<HomeScreen> {
 
   Future<void> _pickFolder() async {
     try {
-      final result = await FilePicker.platform.getDirectoryPath(
-        dialogTitle: 'Select a folder containing Claude session files',
+      final home = _getRealHome() ?? '';
+      final result = await NativePicker.getDirectoryPath(
+        initialDirectory: '$home/.claude/projects',
       );
       if (result != null) {
         _pathController.text = result;
@@ -407,13 +408,13 @@ class _HomeScreenState extends State<HomeScreen> {
 
   Future<void> _loadSingleFile() async {
     try {
-      final result = await FilePicker.platform.pickFiles(
-        type: FileType.custom,
+      final home = _getRealHome() ?? '';
+      final result = await NativePicker.pickFile(
         allowedExtensions: ['jsonl'],
-        dialogTitle: 'Select a Claude session file (.jsonl)',
+        initialDirectory: '$home/.claude/projects',
       );
-      if (result != null && result.files.single.path != null) {
-        await _loadFile(result.files.single.path!);
+      if (result != null) {
+        await _loadFile(result);
       }
     } catch (e) {
       debugPrint('[Load] Error: $e');

lib/services/native_picker.dart

@@ -0,0 +1,41 @@
+import 'package:flutter/services.dart';
+
+/// Native file picker that shows hidden files/folders on macOS.
+/// Uses a custom method channel to NSOpenPanel with showsHiddenFiles = true,
+/// which the file_picker package hardcodes to false.
+class NativePicker {
+  static const _channel = MethodChannel('com.svrnty.native_picker');
+
+  /// Opens a folder picker that shows hidden directories.
+  /// Returns the selected folder path, or null if cancelled.
+  static Future<String?> getDirectoryPath({String? initialDirectory}) async {
+    try {
+      return _channel.invokeMethod<String?>('getDirectoryPath', {
+        'initialDirectory': initialDirectory,
+      });
+    } on PlatformException catch (e) {
+      throw Exception('Native picker error: ${e.message}');
+    }
+  }
+
+  /// Opens a file picker that shows hidden files, filtered to specific extensions.
+  /// Returns the selected file path, or null if cancelled.
+  static Future<String?> pickFile({
+    List<String> allowedExtensions = const [],
+    String? initialDirectory,
+  }) async {
+    try {
+      final result = await _channel.invokeMethod<List?>('pickFiles', {
+        'allowMultiple': false,
+        'allowedExtensions': allowedExtensions,
+        'initialDirectory': initialDirectory,
+      });
+      if (result != null && result.isNotEmpty) {
+        return result.first as String;
+      }
+      return null;
+    } on PlatformException catch (e) {
+      throw Exception('Native picker error: ${e.message}');
+    }
+  }
+}