Add Airweave Search Tool

[EwanTauran]

Summary

Adds two new tools for searching across connected data sources via Airweave:

• AirweaveSearchTool - Basic semantic search
• AirweaveAdvancedSearchTool - Advanced search with filtering and AI reranking

What is Airweave?

Open-source platform providing unified search across 50+ data sources (Stripe, GitHub, Notion, Slack, etc.) with semantic search capabilities.

Changes

• Added crewai_tools/tools/airweave_tool/ with both tools
• Comprehensive README with examples and use cases
• 18 unit tests with full coverage
• Added airweave-sdk to optional dependencies
• Updated package exports

Implementation

• Mirrors Airweave Python SDK design (search() and search_advanced())
• Full async support (_run() and _arun())
• Follows all CrewAI tool patterns (BaseTool, Pydantic schemas, env vars)
• Type-safe with comprehensive error handling

Testing

pytest tests/tools/airweave_tool_test.py

All 18 tests passing. No linting errors.

Related Issue

Closes issue #482