feat: enhance AgentLayout and ChatProvider for improved message handling

- Updated AgentLayout to integrate a new ChatProvider for better message management and interaction.
- Refactored message handling logic to utilize the ChatProvider, allowing for streamlined message processing and state management.
- Introduced Equatable conformance to Source enum for improved comparison in SwiftUI.
- Enhanced the initialization of AgentLayout to support additional configuration options, including callbacks for message changes.
- Added comprehensive tests to validate the new ChatProvider functionality and ensure robust message handling across various scenarios.

Author: sirily11

Sources/Agent/AgentClient.swift

@@ -24,7 +24,7 @@ public enum AgentClientError: LocalizedError {
     }
 }
 
-public enum Source: Identifiable, Sendable {
+public enum Source: Identifiable, Sendable, Equatable {
     case openAI(client: OpenAIClient, models: [Model])
     case openRouter(client: OpenRouterClient, models: [Model])
 
@@ -35,6 +35,11 @@ public enum Source: Identifiable, Sendable {
         }
     }
 
+    public static func == (lhs: Source, rhs: Source) -> Bool {
+        // Compare by id and models for SwiftUI change detection
+        lhs.id == rhs.id && lhs.models == rhs.models
+    }
+
     public var displayName: String {
         switch self {
         case .openAI: return "OpenAI"

Sources/Agent/chat/openaiClient.swift

@@ -83,7 +83,11 @@ public actor OpenAIClient: ChatClient {
 
     public static let defaultBaseURL = URL(string: "https://api.openai.com/v1")!
 
-    public init(apiKey: String, baseURL: URL? = nil) {
+    public init(
+        apiKey: String = ProcessInfo.processInfo.environment["OPENAI_API_KEY"] ?? "",
+        baseURL: URL? = URL(
+            string: ProcessInfo.processInfo.environment["OPENAI_API_BASE_URL"] ?? "")
+    ) {
         self.apiKey = apiKey
         self.baseURL = baseURL ?? Self.defaultBaseURL
     }
@@ -165,10 +169,11 @@ public actor OpenAIClient: ChatClient {
                             if let json = try? JSONDecoder().decode(StreamChunk.self, from: data),
                                 let choice = json.choices.first
                             {
-                                continuation.yield(StreamDelta(
-                                    delta: choice.delta,
-                                    finishReason: choice.finishReason
-                                ))
+                                continuation.yield(
+                                    StreamDelta(
+                                        delta: choice.delta,
+                                        finishReason: choice.finishReason
+                                    ))
                             }
                         }
                     }