Smithery is no longer a supported deployment mode. Remove all Smithery-specific
code paths, middleware, configuration, and tests. This simplifies the codebase
by eliminating DeploymentMode enum, SmitheryConfigMiddleware, session config
context variables, and the smithery_main entrypoint.
Files deleted: Dockerfile.smithery, smithery.yaml, smithery_main.py
ADR-016 retained with deprecated status for historical reference.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
