Add Memanto long-term memory example for CodeAgent

[Neelpatel1604]

Summary

• Adds a new examples/memanto/ example showing how to integrate Memanto persistent memory with smolagents using custom Tool classes (same pattern as examples/rag_using_chromadb.py).
• Includes a thin HTTP client (MemantoClient) for the Memanto REST API, smolagents tools for recall_memory / remember / optional answer_from_memory, and a runnable demo script.
• Adds mocked unit tests in tests/test_memanto_tools.py (no live Memanto server required in CI).
• Demo supports OpenAI, LiteLLM/Groq, and Hugging Face Inference via env vars; seeds demo memory only on empty namespaces to avoid duplicates.

What's included

File	Description
examples/memanto/memanto_client.py	HTTP wrapper: activate session, recall, recall_recent, remember, answer
examples/memanto/memanto_tools.py	MemantoRecallTool, MemantoRememberTool, MemantoAnswerTool, create_memanto_tools()
examples/memanto/memanto_memory_agent.py	Runnable demo with --seed and --task CLI flags
examples/memanto/README.md	Setup and usage documentation
examples/memanto/requirements.txt	Example deps (httpx, python-dotenv)
tests/test_memanto_tools.py	9 unit tests with mocked HTTP/client calls

Why custom Tools instead of MCP?

smolagents already supports MCP, but a dedicated Python example is clearer for users who want:

• Explicit control over which memory operations are exposed
• No MCP subprocess lifecycle to manage
• A pattern consistent with existing RAG examples in this repo

Memanto handles cross-session long-term memory; a separate LLM (OpenAI, HF, etc.) is still required for agent reasoning.

Test plan

• pytest tests/test_memanto_tools.py -v - 9 tests pass (mocked)
• Manual run with memanto serve + OpenAI (OPENAI_API_KEY):

  memanto agent create smolagents-demo
  memanto serve
  python examples/memanto/memanto_memory_agent.py

• Verified agent calls recall_memory and returns stored preference
• Verified duplicate seeding is skipped on subsequent runs (--seed to force)

Prerequisites for reviewers trying the example

pip install -e .
pip install -r examples/memanto/requirements.txt
pip install memanto
memanto agent create smolagents-demo
memanto serve
export OPENAI_API_KEY=...
python examples/memanto/memanto_memory_agent.py