Plugin adapters in molecule-skill-* repos do:
from plugins_registry.builtins import AgentskillsAdaptor as Adaptor
But _load_module_from_path() used exec_module() with a fresh module
namespace that did NOT have plugins_registry or its submodules in sys.modules,
causing:
ModuleNotFoundError: No module named 'plugins_registry'
Fix: before exec_module(), import and register plugins_registry + all three
submodules (builtins, protocol, raw_drop) in sys.modules so adapter imports
resolve correctly. Follows the Option 1 recommendation from issue #296.
Also adds test_resolve_plugin.py verifying the fix for both the
AgentskillsAdaptor import and the full InstallContext/resolve/protocol import.
Closes#296.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
