Add app source and tests

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

lib/Peach/see/configuration/ConnectConfiguration.dart

@@ -0,0 +1,16 @@
+import '../../about/external/data/EnvCheck.dart';
+
+abstract class ConnectConfiguration {
+  /// The environment scan finished: the detected package manager and the
+  /// version string found for each tool (empty when absent).
+  void onEnvironmentProbed(String packageManager, Map<String, String> versions);
+
+  /// The scan failed.
+  void onProbeFailed(String message);
+
+  /// The exact command that would install [tool], for the user to confirm.
+  void onInstallCommandReady(EnvTool tool, String command);
+
+  /// [tool] finished installing; [version] is its freshly re-probed version.
+  void onToolInstalled(EnvTool tool, String version);
+}