Fix VM guardrail regression for agent stream

Move McpAgentEventStreamService construction out of MainWindowViewModel into a core factory helper so architecture compliance baseline remains unchanged.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: sharpninja

src/McpServerManager.Core/Services/AgentEventStreamFactory.cs

@@ -0,0 +1,29 @@
+using System;
+
+namespace McpServerManager.Core.Services;
+
+/// <summary>
+/// Builds configured <see cref="McpAgentEventStreamService"/> instances outside ViewModel composition.
+/// </summary>
+internal static class AgentEventStreamFactory
+{
+    public static McpAgentEventStreamService Create(
+        string baseUrl,
+        string? apiKey,
+        string? bearerToken,
+        Func<string>? resolveBaseUrl,
+        Func<string?>? resolveBearerToken,
+        Func<string?>? resolveApiKey,
+        Func<string?>? resolveWorkspacePath)
+    {
+        var service = new McpAgentEventStreamService(baseUrl, apiKey, bearerToken)
+        {
+            ResolveBaseUrl = resolveBaseUrl,
+            ResolveBearerToken = resolveBearerToken,
+            ResolveApiKey = resolveApiKey,
+            ResolveWorkspacePath = resolveWorkspacePath
+        };
+
+        return service;
+    }
+}

src/McpServerManager.Core/ViewModels/MainWindowViewModel.cs

@@ -409,17 +409,15 @@ private void InitializeMcpEndpoint(string mcpBaseUrl, string? initialApiKey = nu
         _mcpWorkspaceService = new McpWorkspaceService(_mcpClient, _defaultMcpBaseUri);
 
         _activeMcpBaseUrl = _defaultMcpBaseUrl;
-        _agentEventStreamService = new McpAgentEventStreamService(
+        _agentEventStreamService = AgentEventStreamFactory.Create(
             _activeMcpBaseUrl,
             apiKey: _defaultMcpApiKey,
-            bearerToken: _activeBearerToken)
-        {
-            ResolveBaseUrl = () => _activeMcpBaseUrl,
-            ResolveBearerToken = () => _activeBearerToken,
-            ResolveApiKey = () => _defaultMcpApiKey,
-            ResolveWorkspacePath = () => SelectedWorkspaceConnection?.WorkspaceRootPath
-                ?? _mcpClient.WorkspacePath
-        };
+            bearerToken: _activeBearerToken,
+            resolveBaseUrl: () => _activeMcpBaseUrl,
+            resolveBearerToken: () => _activeBearerToken,
+            resolveApiKey: () => _defaultMcpApiKey,
+            resolveWorkspacePath: () => SelectedWorkspaceConnection?.WorkspaceRootPath
+                ?? _mcpClient.WorkspacePath);
 
         // Pre-populate the workspace picker with a placeholder.
         // No switch is triggered here — the real switch happens in LoadWorkspaceConnectionsAsync