Add a Page tab that keeps the last shown page reachable

mac/Sources/Byre/Store.swift

@@ -3,10 +3,10 @@ import Observation
 import SwiftData
 
 enum TaskTab: String {
-    case transcript, board, changes, files, terminal, workflow, project
+    case transcript, board, changes, files, page, terminal, workflow, project
 }
 
-let taskTabs: [TaskTab] = [.transcript, .board, .changes, .files, .terminal, .workflow, .project]
+let taskTabs: [TaskTab] = [.transcript, .board, .changes, .files, .page, .terminal, .workflow, .project]
 
 enum JumpTarget: Equatable {
     case question(String)
@@ -71,6 +71,7 @@ final class Store {
     var connected = false
     private(set) var focus = Focus()
     var sheet: Sheet?
+    var shownPages: [String: Page] = [:]
     var leadSessions: [AgentSession] = []
     let leadFeed: Feed
     var jump: Jump?