Theme system overhaul, UI polish, and VS2022 Dark theme

- Replaced hardcoded theme factories with JSON files + CMake build step
- Shared ThemeFieldMeta table for DRY serialization and editor UI
- Fixed live preview (auto-triggers on color change, no toggle button)
- Fixed duplicate theme entries when editing built-in themes
- Moved title bar from icon to bold "Reclass" text with View > Show Icon toggle
- MDI tabs: 24px height, unicode close button styled like TypeSelectorPopup
- Added VS2022 Dark theme with purple accent colors
- Status bar padding, removed monospace font overrides on tabs/statusbar
- Default startup opens Ball demo + Unnamed hex64 tabs

src/themes/theme.h

@@ -48,9 +48,18 @@ struct Theme {
 
     QJsonObject toJson() const;
     static Theme fromJson(const QJsonObject& obj);
-
-    static Theme reclassDark();
-    static Theme warm();
 };
 
+// ── Shared field metadata (serialization + editor UI) ──
+
+struct ThemeFieldMeta {
+    const char*    key;     // JSON key
+    const char*    label;   // display label
+    const char*    group;   // section group name
+    QColor Theme::*ptr;
+};
+
+extern const ThemeFieldMeta kThemeFields[];
+extern const int kThemeFieldCount;
+
 } // namespace rcx