Add lightweight MemoryTool with optional Qdrant backend

[MagellaX]

Summary

• introduce a MemoryTool that defaults to an in-memory store for quick add/search
• optionally switch to Qdrant + sentence-transformers when QDRANT_URL is set
• expose it via hud.tools and cover the in-memory path with async unit tests

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Note

Introduces a lightweight MemoryTool with in-memory storage and optional Qdrant-based vector search, exported via hud.tools, with unit tests.

• Tools:
  • MemoryTool: Add/search short-term memory; defaults to token-overlap InMemoryStore; optional QdrantBackend with sentence-transformers embeddings.
• Exposure:
  • Export MemoryTool in hud/tools/__init__.py.
• Tests:
  • Add tests for InMemoryStore querying, MemoryTool add/search, and unknown action handling.

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