fix: share private chat files and harden native lifecycle

Sources/Chat/ChatStore.swift

@@ -22,6 +22,7 @@ final class ChatStore: ObservableObject {
     @Published var researchAvailable = false
     @Published var research = false
     @Published var exportText: String?
+    @Published var exportFile: PrivateChatExport?
     private var syncCursor = 0
     private var syncTask: Task<Void, Never>?
     @Published var model = ""
@@ -41,7 +42,7 @@ final class ChatStore: ObservableObject {
     var activeRun: HopeRun? { runs.first(where: \.active) }
 
     init(api: ChatTransport) { self.api = api; self.features = ChatFeatureStore(api: api) }
-    deinit { stream?.cancel() }
+    deinit { stream?.cancel(); syncTask?.cancel() }
     private func call<T: Decodable>(_ path: String, method: String = "GET", body: [String: Any]? = nil, query: [URLQueryItem] = []) async throws -> T {
         let epoch = generation
         let data = try await api.request(path, method: method, body: body, query: query)
@@ -77,7 +78,7 @@ final class ChatStore: ObservableObject {
     func open(_ conversation: HopeConversation) async {
         if let selected { drafts[selected.id] = draft }
         generation += 1; stream?.cancel(); stream = nil
-        selected = conversation; messages = []; runs = []; progress = nil; approval = nil
+        selected = conversation; messages = []; runs = []; progress = nil; approval = nil; exportText = nil; exportFile = nil
         draft = drafts[conversation.id] ?? ""; pendingKey = nil; selectedAttachmentIds = []; olderMessagesCursor = nil; error = nil
         do {
             let detail: ConversationDetail = try await call("api/conversations/\(conversation.id)")
@@ -249,16 +250,20 @@ final class ChatStore: ObservableObject {
             let bytes = try await api.request("api/conversations/\(selected.id)/export", method: "GET", body: nil, query: [URLQueryItem(name: "format", value: format)])
             guard epoch == generation, !closed else { return }
             exportText = String(data: bytes, encoding: .utf8)
+            exportFile = PrivateChatExport(data: bytes, filename: "Hope-chat-\(selected.id).\(format == "json" ? "json" : "md")", type: format == "json" ? .json : .plainText)
         } catch { await failure(error) }
     }
     func foreground(_ active: Bool) {
         syncTask?.cancel(); syncTask = nil
-        guard active, !closed else { return }
+        guard active, !closed else { stream?.cancel(); stream = nil; return }
+        resume()
         syncTask = Task { [weak self] in
-            guard let self else { return }
-            await loadResearch()
-            while !Task.isCancelled, !closed {
-                await synchronize()
+            await self?.loadResearch()
+            while !Task.isCancelled {
+                guard self?.closed == false else { return }
+                await self?.synchronize()
+                // Release the store before suspension; its retained task must not
+                // keep an otherwise-discarded account alive indefinitely.
                 do { try await Task.sleep(for: .seconds(5)) } catch { return }
             }
         }
@@ -296,7 +301,7 @@ final class ChatStore: ObservableObject {
         } catch { if case ChatFailure.status(let status) = error, status == 401 || status == 403 { await failure(error) } }
     }
     /// Invalidate every outstanding callback before clearing account-visible content.
-    func close() { syncTask?.cancel(); syncTask = nil; exportText = nil; research = false; features.close(); selectedAttachmentIds = []; closed = true; generation += 1; stream?.cancel(); stream = nil; api.cancel(); conversations = []; workspaces = []; selected = nil; messages = []; runs = []; draft = ""; drafts = [:]; cursors = [:]; pendingKey = nil; approval = nil; progress = nil; error = nil }
+    func close() { syncTask?.cancel(); syncTask = nil; exportText = nil; exportFile = nil; research = false; features.close(); selectedAttachmentIds = []; closed = true; generation += 1; stream?.cancel(); stream = nil; api.cancel(); conversations = []; workspaces = []; selected = nil; messages = []; runs = []; draft = ""; drafts = [:]; cursors = [:]; pendingKey = nil; approval = nil; progress = nil; error = nil }
 }
 struct ChatModelChoice: Decodable, Identifiable { let id: String; let thinkingLevels: [String]? }
 struct ChatSettingsValue: Decodable { let model: String; let thinkingLevel: String }