Split Planning and Execution: o3 Planner, GPT-4o Executor

Production reasoning guides recommend decoupling planning from execution: use o1 or o3 to devise strategic plans (and invoke them as a "Re-Planner Node" only if an executor encounters an unrecoverable runtime exception or contradictory state), while delegating fast tool execution to lower-latency models like GPT-4o.

o3 Re-Planner Node Prompt: The GPT-4o executor encountered an unrecoverable runtime exception at step 4: {{ERROR_TRACE}}. Given the current state {{STATE}}, backtrack from the failed branch and output a revised strategic plan JSON for the executor.