Add todo CRUD tab in companion app

IrisCompanion/iris/ViewModels/TodosViewModel.swift

@@ -0,0 +1,73 @@
+//
+//  TodosViewModel.swift
+//  iris
+//
+//  Created by Codex.
+//
+
+import Foundation
+
+@MainActor
+final class TodosViewModel: ObservableObject {
+    @Published private(set) var todos: [TodoItem] = []
+    @Published var newTitle: String = ""
+
+    private let store: TodoStore
+
+    init(store: TodoStore = TodoStore()) {
+        self.store = store
+        refresh()
+    }
+
+    func refresh() {
+        todos = sortedItems(store.snapshot())
+    }
+
+    func addTodo() {
+        let trimmed = normalizedTitle(newTitle)
+        guard !trimmed.isEmpty else { return }
+        store.add(title: trimmed)
+        newTitle = ""
+        refresh()
+    }
+
+    func deleteTodo(id: UUID) {
+        store.delete(id: id)
+        refresh()
+    }
+
+    func toggleCompleted(id: UUID) {
+        guard let current = todos.first(where: { $0.id == id }) else { return }
+        store.setCompleted(id: id, completed: !current.isCompleted)
+        refresh()
+    }
+
+    func updateTitle(id: UUID, title: String) {
+        let trimmed = normalizedTitle(title)
+        guard !trimmed.isEmpty else { return }
+        store.updateTitle(id: id, title: trimmed)
+        refresh()
+    }
+
+    private func normalizedTitle(_ raw: String) -> String {
+        raw.trimmingCharacters(in: .whitespacesAndNewlines)
+    }
+
+    private func sortedItems(_ items: [TodoItem]) -> [TodoItem] {
+        items.sorted { lhs, rhs in
+            if lhs.isCompleted != rhs.isCompleted {
+                return !lhs.isCompleted
+            }
+            if lhs.isCompleted {
+                let lhsDate = lhs.completedAt ?? lhs.updatedAt
+                let rhsDate = rhs.completedAt ?? rhs.updatedAt
+                if lhsDate != rhsDate {
+                    return lhsDate > rhsDate
+                }
+            } else if lhs.createdAt != rhs.createdAt {
+                return lhs.createdAt > rhs.createdAt
+            }
+            return lhs.id.uuidString < rhs.id.uuidString
+        }
+    }
+}