feat: restart MCP servers on /mcp refresh (#5479)

Co-authored-by: Brian Ray <62354532+emeryray2002@users.noreply.github.com>
Co-authored-by: N. Taylor Mullen <ntaylormullen@google.com>

packages/cli/src/ui/hooks/atCommandProcessor.test.ts

@@ -63,6 +63,12 @@ describe('handleAtCommand', () => {
         isPathWithinWorkspace: () => true,
         getDirectories: () => [testRootDir],
       }),
+      getMcpServers: () => ({}),
+      getMcpServerCommand: () => undefined,
+      getPromptRegistry: () => ({
+        getPromptsByServer: () => [],
+      }),
+      getDebugMode: () => false,
     } as unknown as Config;
 
     const registry = new ToolRegistry(mockConfig);