feat(studio): brand-agnostic onboarding hints + clickable checklist + theme-picker clarity

Three changes:

1. Onboarding checklist hints no longer mention DeepWiki,
   Semgrep, text.extract, or extract-summarize.yaml by
   name. Brand- and file-specific copy moved to neutral
   feature pointers ('add an MCP source', 'install a
   module'). Brand names belong on the welcome page only
   if they're load-bearing for understanding, which they
   aren't.

2. Checklist rows are now clickable. Tapping a row navigates
   to the page where the operator can complete it — MCP +
   AI open Settings, Module opens Store, Flow opens Flows.
   StudioShellState gains a public navigateTo(pageId) helper
   so descendants can drive sidebar selection without
   plumbing a controller through props.

3. Theme picker hint copy rewritten. Old hint suggested
   'Custom' was a single-colour tweak; new copy spells out
   that Material 3 derives a full palette (primary,
   secondary, tertiary, surface, …) from one seed colour.
   The Custom tile shows a small tune icon so its
   open-the-picker semantics is visually distinct from the
   apply-immediately plugin tiles.

Editor bumped to 0.12.0 (panel toggle + LabVIEW-style port
colours).

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

lib/main.dart

@@ -227,15 +227,31 @@ class StudioShell extends StatefulWidget {
   const StudioShell({super.key});
 
   @override
-  State<StudioShell> createState() => _StudioShellState();
+  State<StudioShell> createState() => StudioShellState();
 }
 
-class _StudioShellState extends State<StudioShell> {
+class StudioShellState extends State<StudioShell> {
   int _selectedIndex = 0;
   bool? _connected; // null = unknown, polled on a timer
   String? _activeChannel; // local / dev / beta / production
   Timer? _healthPoll;
 
+  /// Switch the sidebar's selected page by its registered id
+  /// (`store`, `flows`, `audit`, etc.). Used by the welcome
+  /// page's onboarding checklist to make each item a real
+  /// navigation hop instead of a static hint. Silently
+  /// ignores unknown ids.
+  void navigateTo(String pageId) {
+    final idx = _pages.indexWhere((p) => p.id == pageId);
+    if (idx < 0) return;
+    setState(() => _selectedIndex = idx);
+  }
+
+  /// Lookup helper — descendants call this to drive nav
+  /// without holding a controller reference.
+  static StudioShellState? of(BuildContext context) =>
+      context.findAncestorStateOfType<StudioShellState>();
+
   static const _pages = <_NavPage>[
     _NavPage(
       id: 'welcome',