feat: allow custom filename for context files (#654)

Co-authored-by: N. Taylor Mullen <ntaylormullen@google.com>

packages/cli/src/config/settings.ts

@@ -30,6 +30,7 @@ export interface Settings {
   mcpServerCommand?: string;
   mcpServers?: Record<string, MCPServerConfig>;
   showMemoryUsage?: boolean;
+  contextFileName?: string;
   // Add other settings here.
 }