chore: define view model (#12949)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **New Features**
* Introduced a chat interface with message list, empty state view, and
support for user, assistant, and system messages.
* Added a chat manager for session and message handling, including
session creation, message sending, and error management.
* Implemented various chat cell types (attachments, context references,
workflow status, loading, and error cells) with corresponding data
models and view models.
* Enabled asynchronous message sending from the input box with error
alerts and automatic session creation.
* Added workflow and context-related models for advanced chat features.

* **Enhancements**
* Improved UI responsiveness with table view updates and dynamic empty
state handling.
  * Provided a method to clear all attachments in the input box.

* **Bug Fixes / Style**
* Refined code formatting, access control, and minor stylistic
improvements across multiple files for consistency.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/frontend/apps/ios/App/App/Mutex.swift

@@ -8,15 +8,15 @@
 import Foundation
 
 final class Mutex<Wrapped>: @unchecked Sendable {
-  private let lock = NSLock.init()
+  private let lock = NSLock()
   private var wrapped: Wrapped
-  
+
   init(_ wrapped: Wrapped) {
     self.wrapped = wrapped
   }
-  
+
   func withLock<R>(_ body: @Sendable (inout Wrapped) throws -> R) rethrows -> R {
-    self.lock.lock()
+    lock.lock()
     defer { self.lock.unlock() }
     return try body(&wrapped)
   }