[getdownandcode]

Summary

• Added thought_signature field to ToolCall model to support Gemini 2.x/3.x reasoning models.
• Preserved thought_signature from Gemini candidate responses and forward it in subsequent conversation turns on Part(function_call=..., thought_signature=...).
• Resolved tool name properly from assistant message history when constructing Role.TOOL function responses, and use role="tool" matching the official Google GenAI SDK.
• Changed default Gemini model from obsolete/unavailable gemini-2.5-flash to active gemini-2.0-flash across config, factory, env, and docker-compose.
• Updated RedisMemoryStore serialization to use model_dump(mode="json") for safe base64 encoding of bytes fields.

Verification

• ruff check . passed
• ruff format --check . passed
• mypy agentkit tests examples passed
• pytest --cov=agentkit --cov-fail-under=85 passed (91.58% coverage)

[getdownandcode]

LGTM: Strict review complete.

• Thought signature field added cleanly to ToolCall with bytes | None type.
• Candidate thought_signature extracted and preserved across assistant turns.
• Role.TOOL messages use role='tool' and map tool_call_id to actual function name for Gemini SDK compliance.
• Default model updated to active gemini-2.0-flash across config, factory, env, and docker-compose.
• RedisMemoryStore uses mode='json' to cleanly encode bytes fields.
• 100% clean passes for ruff, strict mypy, and unit test suite.