chore: improve project health and memory safety

[wxai-space]

Summary

• add CI, issue templates, PR template, security policy, contribution guide, and code of conduct
• update repository/PyPI metadata and replace old wxai-space links across README files
• add v0.6.5 README news and correct outdated lightweight/dependency wording
• align dependency metadata with runtime imports (openai<2, PyYAML, boto3)
• add MemoryPolicy for namespace-based memory isolation and provenance filtering
• remove stream tool-call debug print and harden dynamic tool name/path handling
• classify current open issues with priority and type labels

Compatibility

• default memory behavior remains compatible unless a MemoryPolicy or memory_namespace is configured
• default agent.run() and stream=True behavior are unchanged
• no tools, dist artifacts, backup files, or legacy local tests are included

Tests

• python -m compileall -q LightAgent tests/test_v065_core.py tests/test_v070_tracing.py tests/test_memory_policy.py
• PYTHONPATH=. python -m pytest -q tests/test_v065_core.py tests/test_v070_tracing.py tests/test_memory_policy.py
• GitHub Actions CI: Python 3.10, 3.11, 3.12 pass

Notes

• This PR intentionally includes .github files because project-health P0 includes CI and collaboration templates.
• The branch was generated through the GitHub Contents API, so squash merge is recommended.