bug: AgentState uses __dunder__ keys which can clash with Python internals

[QuantumByte-01]

Problem

AgentState TypedDict uses double-underscore keys:

"__start_number__": 1,
"__previous_text__": "",

Python reserves __dunder__ names for special methods and attributes. While this works today, it's non-standard for TypedDict and could cause unexpected behavior with introspection tools, serialization, or future Python versions.

Fix

Rename to regular keys: start_number and previous_text.

[pragati-0208]

Hi, I’d like to work on this issue. Could you please assign it to me?