Issue: FINAL VAR resolution broken, Python 3.11 isinstance crashes, and QueryMetadata cannot handle…

Issue: FINAL VAR resolution broken, Python 3.11 isinstance crashes, and QueryMetadata cannot handle…: a task in LegoFlow-SWE (Harbor dataset). The RLM library has several bugs that prevent correct final answer extraction, cause runtime errors on Python 3.11, and throw exceptions when constructing…

The task

The RLM library has several bugs that prevent correct final answer extraction, cause runtime errors on Python 3.11, and throw exceptions when constructing `QueryMetadata` with non‑string prompt data.

Part of Lego-X/LegoFlow-SWE.