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_en.arb

@@ -1,5 +1,19 @@
 {
   "@@locale": "en",
+  "guidedSetupTitle": "Setup assistant",
+  "guidedSetupIntro": "Answer three questions and Ch∆In assembles a tailored config, module set and starter flow.",
+  "guidedSetupScenario": "Scenario",
+  "guidedSetupIntent": "Task",
+  "guidedSetupTarget": "Where will it run?",
+  "guidedSetupApproval": "Require a human approval step before the AI step",
+  "guidedSetupDataLocal": "Data must stay local (air-gapped posture)",
+  "guidedSetupReviewHeading": "This is the plan Ch∆In will apply:",
+  "guidedSetupApply": "Apply setup",
+  "guidedSetupApplied": "Setup applied. Finish with the steps below:",
+  "guidedSetupBack": "Back",
+  "guidedSetupNext": "Next",
+  "guidedSetupCancel": "Cancel",
+  "guidedSetupClose": "Close",
   "appTitle": "Ch∆In Studio",
   "@appTitle": {
     "description": "App-bar title in the OS task switcher."