Replace sys.path.insert hacks in Python agent files with direct
imports via symlinks to shared/{python,typescript}/tools.
Update Dockerfiles, entrypoints, and configs to support the new
symlink-based tool resolution. Add PARITY_NOTES for frameworks
that have known gaps.
The showcase framework directories better reflect their role as
integration examples rather than distributable packages.
Renames showcase/packages/ -> showcase/integrations/ and updates
the test docker-compose file reference accordingly.