Python SDK is live — update all references

[devonartis]

The Python SDK is now live:

• PyPI: https://pypi.org/project/agentwrit/
• GitHub: https://github.com/devonartis/agentwrit-python
• Docker Hub: https://hub.docker.com/r/devonartis/agentwrit-medassist (MedAssist demo)

What needs updating

• docs/python-sdk.md — remove "coming soon", add install instructions (PR Add bandit SAST + pip-audit dependency scan to Python SDK CI #45)
• Verify all cross-repo links resolve
• Update any remaining agentauth references to agentwrit in SDK docs
• Marketing drafts can now reference live SDK (unblocks Week 2+ of launch checklist)