feat: migrate agent core to pydantic-ai framework

core/planning_agent.py

@@ -1,14 +1,14 @@
 import logging
 from core.agent import BaseAgent
 from core.prompts import PLANNING_AGENT_SYSTEM_PROMPT
+from core.schemas import ExecutionPlan
 
 logger: logging.Logger = logging.getLogger("agent-planning")
 
 
 class PlanningAgent(BaseAgent):
-    """AI agent that analyzes a PR/issue and builds an implementation plan."""
+    """AI agent that analyzes a PR/issue and builds an implementation plan using Pydantic AI."""
 
     def __init__(self, model_name: str) -> None:
         super().__init__(model_name)
         self.system_prompt: str = PLANNING_AGENT_SYSTEM_PROMPT
-