1. infrastructure/__init__.py: remove nonexistent get_ssh_pool import,
use lazy __getattr__ to avoid triggering MySQL engine at import time
2. auth_service.py + auth_jwt.py: JWT sub field must be string
(PyJWT 2.12+ enforces RFC 7519), decode with int() conversion
3. session.py: lazy engine init — engine created on first access
instead of module import time, allows testing without MySQL
4. Tests: fix Column default assertions (SQLAlchemy defaults only
apply on DB INSERT), fix Request.url mock for Starlette
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Nexus Agent