feat(studio): rich theme picker (presets + custom colour) + editor 0.11.0

Settings dialog's Theme Plugin section is now a grid of
swatched tiles:

- Built-in (none) — falls back to FaiTheme.light/.dark
- One tile per installed studio.theme.* plugin, each
  showing the plugin's primary/secondary/tertiary as
  live colour dots. Tile loads its preview lazily so a
  dozen installed themes don't block the picker.
- Custom — opens a colour-picker dialog with 12 curated
  Material presets + a hex input + live preview. Selecting
  applies ColorScheme.fromSeed for both brightnesses.

main.dart's _pluginThemes parses a 'custom:#RRGGBB' sigil
in the same notifier slot as plugin capability ids, so the
existing persistence + restoration paths cover the custom
case with no new state.

Bumps editor to 0.11.0 (type-checked port connections +
dynamic card width fix + card-height border allowance) and
Studio to 0.58.0.

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

lib/data/registry_token.dart

@@ -10,7 +10,8 @@ import 'package:path/path.dart' as p;
 /// requires the operator to fiddle with shell env vars.
 class RegistryToken {
   static String _faiHome() {
-    final home = Platform.environment['HOME'] ?? Platform.environment['USERPROFILE'];
+    final home =
+        Platform.environment['HOME'] ?? Platform.environment['USERPROFILE'];
     if (home == null || home.isEmpty) {
       throw StateError('Cannot resolve home directory (no HOME / USERPROFILE)');
     }