fix(settings): reveal System-AI test result + refresh onboarding checklist

Two settings bugs the operator hit:

1. 'Test connection' appeared to do nothing. The result/error panel
   renders at the bottom of the System-AI editor's scrollable,
   600px-capped form, so on a tall dialog it lands below the fold —
   the footer button flickers 'Testing…' and nothing visible changes.
   The editor now holds a ScrollController and animates the content
   to reveal the outcome whenever a test result or error appears.

2. The welcome onboarding checklist kept 'connect System-AI'
   unchecked right after saving a working config. The checklist row
   opens the Settings dialog (an overlay, not a navigation), and on
   close the checklist never re-probed — so it showed the stale
   pre-config state. Both settings-opening rows (System-AI, MCP) now
   re-probe when the dialog closes; navigation-based rows already
   self-heal on return.

Studio suite green; flutter analyze clean.

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

lib/pages/welcome.dart

@@ -641,6 +641,18 @@ class _OnboardingChecklistState extends State<_OnboardingChecklist> {
     setState(() => _dismissed = true);
   }
 
+  /// Open Settings (where System-AI + MCP are configured) and
+  /// re-probe when it closes. The Settings dialog overlays the
+  /// welcome page rather than navigating, so without this the
+  /// checklist kept showing the pre-config state (e.g. "connect
+  /// System-AI" stayed unchecked right after saving a working
+  /// config). Navigation-based rows self-heal on return; these
+  /// dialog-based ones did not.
+  Future<void> _openSettingsThenRefresh() async {
+    await ChainSettingsDialog.show(context);
+    if (mounted) await _refresh();
+  }
+
   /// Localized plain-language label for the applied setup profile.
   String _profileLabel(AppLocalizations l) => switch (_setupProfile) {
     'enterprise' => l.setupProfileEnterprise,
@@ -664,13 +676,13 @@ class _OnboardingChecklistState extends State<_OnboardingChecklist> {
         _aiOk,
         l.welcomeChecklistAi,
         l.welcomeChecklistAiHint,
-        () => ChainSettingsDialog.show(context),
+        _openSettingsThenRefresh,
       ),
       (
         _mcpOk,
         l.welcomeChecklistMcp,
         l.welcomeChecklistMcpHint,
-        () => ChainSettingsDialog.show(context),
+        _openSettingsThenRefresh,
       ),
       (
         _moduleOk,