docs: add ClawMem memory adapter example

[helloJamest]

Summary

• add a dependency-free ClawMemMemoryAdapter example that satisfies LightAgent's MemoryProtocol
• document how LightAgent memory writes map to ClawMem-style knowledge items while preserving MemoryScope metadata
• add fake-client tests so the example is covered without live network calls, secrets, or a required ClawMem dependency

Why

Issue #33 asks for an optional ClawMem-backed memory path that stays outside the core dependency set. This PR keeps the integration as an example/docs/test contribution: applications can wrap their ClawMem HTTP, MCP, SDK, or local client behind the tiny create_memory / search_memories surface while LightAgent continues to use store(data, user_id) and retrieve(query, user_id).

Refs #33.

Validation

• python -m pytest -q tests/test_clawmem_memory_adapter_example.py (3 passed)
• python -m pytest -q tests/test_clawmem_memory_adapter_example.py tests/test_vector_memory_adapter_example.py tests/test_memory_policy.py tests/test_shared_memory_pool.py (23 passed)
• python -m pytest -q (69 passed)
• python -m compileall -q LightAgent example tests
• git diff --check