Scaffold: package, settings, errors, server factory, shared contracts

protocol/types.py and arsdk/types.py are the interfaces the parallel streams
build against: command/arg/enum/expectation specs and the safety tiers on one
side, frame encoding and the buffer conventions on the other.

Logging goes to stderr throughout, since stdout carries JSON-RPC. That is also
why this package will speak ARSDK itself rather than through pyparrot, which
prints from its receive thread.

.gitignore

@@ -0,0 +1,7 @@
+.venv/
+__pycache__/
+.ruff_cache/
+.pytest_cache/
+dist/
+captures/
+*.egg-info/