Implement --save-session functionality with session logging

Co-authored-by: pavelfeldman <883973+pavelfeldman@users.noreply.github.com>

config.d.ts

@@ -90,6 +90,11 @@ export type Config = {
    */
   saveTrace?: boolean;
 
+  /**
+   * Whether to save the session log with tool calls and snapshots into the output directory.
+   */
+  saveSession?: boolean;
+
   /**
    * The directory to save output files.
    */