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/Models/SystemStatusModels.swift b/Hutch/Models/SystemStatusModels.swift
index 9a664b0..ddd659c 100644
--- a/Hutch/Models/SystemStatusModels.swift
+++ b/Hutch/Models/SystemStatusModels.swift
@@ -1,6 +1,6 @@
 import Foundation
 
-enum StatusLevel: String, Codable, Sendable {
+nonisolated enum StatusLevel: String, Codable, Sendable {
     case operational
     case degraded
     case majorOutage
@@ -32,7 +32,7 @@ enum StatusLevel: String, Codable, Sendable {
     }
 }
 
-struct StatusServiceState: Identifiable, Hashable, Codable, Sendable {
+nonisolated struct StatusServiceState: Identifiable, Hashable, Codable, Sendable {
     let id: String
     let name: String
     let slug: String?
@@ -40,7 +40,7 @@ struct StatusServiceState: Identifiable, Hashable, Codable, Sendable {
     let description: String?
 }
 
-struct StatusIncident: Identifiable, Hashable, Codable, Sendable {
+nonisolated struct StatusIncident: Identifiable, Hashable, Codable, Sendable {
     let id: String
     let title: String
     let summary: String?
@@ -50,7 +50,7 @@ struct StatusIncident: Identifiable, Hashable, Codable, Sendable {
     let isActive: Bool?
 }
 
-struct SystemStatusSnapshot: Hashable, Codable, Sendable {
+nonisolated struct SystemStatusSnapshot: Hashable, Codable, Sendable {
     let services: [StatusServiceState]
     let activeIncidents: [StatusIncident]
     let lastUpdated: Date
@@ -78,7 +78,7 @@ struct SystemStatusSnapshot: Hashable, Codable, Sendable {
     }
 }
 
-struct SystemStatusPageData: Sendable {
+nonisolated struct SystemStatusPageData: Sendable {
     let snapshot: SystemStatusSnapshot
     let recentIncidents: [StatusIncident]
 }