feat(model node): add option to store final response in state with response key

feat(model node): add configurable next target for routing when no tool calls are present

refactor(middleware, vectorstore, viz): introduce default constants for polling intervals and timeouts

Refactor graph and tool packages for improved type handling and middleware removal

Add middleware tests for audit, cache, circuit breaker, guardrail, and timeout

refactor(middleware): replace interface{} with any for improved type safety

feat(middleware): refactor middleware implementation and add new middleware functions

refactor(docs): remove default values from graph key definitions for clarity

feat(graph): implement reflection-free iteration for reducers and enhance state key management

feat(runtime): replace MustNewRuntime with NewRuntime and handle errors in tests

Refactor graph state management with reducer support

feat(openai): implement schema transformation for OpenAI strict mode compliance

feat(reflectutil): add reflection helpers for nil and zero value checks

feat(runtime): implement sharded counter for per-vertex message tracking and update scheduler integration

feat(rag): enhance query rephrasing and context detection for improved conversational handling