feat(studio): guided-setup wizard (reuses chain init engine)

A Welcome 'Setup assistant' button opens a wizard that collects
scenario / intent / target (+ approval & data-local toggles), then calls
`chain init --answers` to preview the assembled plan and `--apply --force`
to write the config — reusing the Rust deterministic engine, no logic
duplicated. New SystemActions.chainInit; copyable errors via
showFaiProcessError; EN+DE l10n. analyze clean; smoke test + existing
welcome/sidebar tests pass.

Signed-off-by: flemming-it <stefan.a.flemming@googlemail.com>

lib/l10n/app_localizations_de.dart

@@ -8,6 +8,51 @@ import 'app_localizations.dart';
 class AppLocalizationsDe extends AppLocalizations {
   AppLocalizationsDe([String locale = 'de']) : super(locale);
 
+  @override
+  String get guidedSetupTitle => 'Setup-Assistent';
+
+  @override
+  String get guidedSetupIntro =>
+      'Beantworte drei Fragen — Ch∆In stellt passende Konfiguration, Modul-Set und Start-Flow zusammen.';
+
+  @override
+  String get guidedSetupScenario => 'Szenario';
+
+  @override
+  String get guidedSetupIntent => 'Aufgabe';
+
+  @override
+  String get guidedSetupTarget => 'Wo läuft es?';
+
+  @override
+  String get guidedSetupApproval =>
+      'Menschlichen Freigabe-Schritt vor dem KI-Schritt verlangen';
+
+  @override
+  String get guidedSetupDataLocal => 'Daten müssen lokal bleiben (air-gapped)';
+
+  @override
+  String get guidedSetupReviewHeading => 'Diesen Plan wird Ch∆In anwenden:';
+
+  @override
+  String get guidedSetupApply => 'Setup übernehmen';
+
+  @override
+  String get guidedSetupApplied =>
+      'Setup übernommen. Schließe mit den Schritten unten ab:';
+
+  @override
+  String get guidedSetupBack => 'Zurück';
+
+  @override
+  String get guidedSetupNext => 'Weiter';
+
+  @override
+  String get guidedSetupCancel => 'Abbrechen';
+
+  @override
+  String get guidedSetupClose => 'Schließen';
+
   @override
   String get appTitle => 'Ch∆In Studio';