Update agent/nodes.py

Update agent/nodes.py

Update agent/nodes.py

Major upgrades: Enhanced web search + multimodal video analysis

Enhanced LLM-first architecture with smart attachment handling

Fix: Converted all relatives imports within agent to refelect agent

Refactor: Add AnswerRefinementNode and WebSearchNode, fix initial setup and duckduckgo-search import. Prepare for further debugging.

Initial clean commit of GAIA agent project (no secrets or large files, .env explicitly ignored)