Generated stubs inject sys.path globally and shadow other packages

[zeevdr]

Description

sdk/src/opendecree/_generated/__init__.py:13-18 calls sys.path.insert at import time, exposing <site-packages>/opendecree/_generated globally. Any other package named centralconfig or v1 in the same environment is shadowed — including the server's own stubs in a shared venv. This is a blocker for shipping the SDK to PyPI.

Acceptance criteria

• Regenerate stubs with absolute imports (from opendecree._generated.centralconfig.v1 import ...) — buf plugin option or post-process step
• Drop the sys.path injection entirely
• Add a test that imports both the SDK and a hypothetical second centralconfig package and asserts no shadowing