Fix Swift 6-mode isolation and attribute warnings

Under SWIFT_DEFAULT_ACTOR_ISOLATION = MainActor these are warnings in Swift 5
mode and errors in Swift 6 mode:

- Drop @retroactive from 'extension LookupType: AppEnum'; LookupType is
  declared in this module, so the attribute never applied.
- Mark SyntaxHighlightTheme and SyntaxHighlighter nonisolated. They were
  inferred @MainActor but are built and used from the nonisolated markdown
  renderers in Task.detached; nonisolated makes the off-main confinement
  correct (Highlightr's JSContext was being driven off the main actor).

1 files changed, 1 insertions, 1 deletions

diff --git a/Hutch/App/HutchIntents.swift b/Hutch/App/HutchIntents.swift
index fe4ebdc..ff8fec8 100644
--- a/Hutch/App/HutchIntents.swift
+++ b/Hutch/App/HutchIntents.swift
@@ -337,7 +337,7 @@ struct CheckBuildsIntent: AppIntent {
 
 // MARK: - Search Type
 
-extension LookupType: @retroactive AppEnum {
+extension LookupType: AppEnum {
     public nonisolated static var typeDisplayRepresentation: TypeDisplayRepresentation {
         TypeDisplayRepresentation(name: "Search Type")
     }