Adopt Swift 6 language mode

Flip SWIFT_VERSION to 6.0 (keeping SWIFT_DEFAULT_ACTOR_ISOLATION = MainActor)
and resolve every resulting diagnostic. Mechanical, no behaviour change:

- Models: pure value types in Models/ and utility extensions (Date, DateFormatter,
  SRHTWebURL) marked nonisolated so the nonisolated networking layer can use them.
- App Intents: stored 'static var' (title/description/openAppWhenRun/
  typeDisplayRepresentation/defaultQuery/caseDisplayRepresentations) -> 'static let';
  drop the invalid @retroactive on the in-module LookupType: AppEnum.
- Sendable dicts: 'nil as String? as Any' -> 'nil as String? as any Sendable'.
- UserDefaults: retroactive @unchecked Sendable (documented thread-safe).
- WidgetKit completion handlers rebound nonisolated(unsafe) to cross into Task {};
  TipStoreViewModel task handle is @ObservationIgnored nonisolated(unsafe) for
  its nonisolated deinit.
- Tests run on @MainActor; a few constant fixtures marked nonisolated for use in
  @Sendable stub closures.

Builds and the full suite are clean in Swift 6 mode. Roadmap updated.

1 files changed, 5 insertions, 5 deletions

diff --git a/Hutch/Views/Settings/SettingsViewModel.swift b/Hutch/Views/Settings/SettingsViewModel.swift
index 8536e60..2d57ba5 100644
--- a/Hutch/Views/Settings/SettingsViewModel.swift
+++ b/Hutch/Views/Settings/SettingsViewModel.swift
@@ -198,9 +198,9 @@ final class SettingsViewModel {
         do {
             let input: [String: any Sendable] = [
                 "email": email,
-                "url": url.isEmpty ? nil as String? as Any : url,
-                "location": location.isEmpty ? nil as String? as Any : location,
-                "bio": bio.isEmpty ? nil as String? as Any : bio
+                "url": url.isEmpty ? nil as String? as any Sendable : url,
+                "location": location.isEmpty ? nil as String? as any Sendable : location,
+                "bio": bio.isEmpty ? nil as String? as any Sendable : bio
             ]
             let result = try await client.execute(
                 service: .meta,
@@ -243,7 +243,7 @@ final class SettingsViewModel {
         do {
             // The input variable has avatar set to null; the actual file
             // is sent as a separate multipart part per graphql-multipart-request-spec.
-            let input: [String: any Sendable] = ["avatar": nil as String? as Any]
+            let input: [String: any Sendable] = ["avatar": nil as String? as any Sendable]
             let result = try await client.executeMultipart(
                 service: .meta,
                 query: Self.updateUserMutation,
@@ -286,7 +286,7 @@ final class SettingsViewModel {
         error = nil
 
         do {
-            let input: [String: any Sendable] = ["avatar": nil as String? as Any]
+            let input: [String: any Sendable] = ["avatar": nil as String? as any Sendable]
             let result = try await client.execute(
                 service: .meta,
                 query: Self.updateUserMutation,