`retry_get_plugin` raises `TypeError` when called for yaml-based interfaces

Requested Update

Description

• When get_yaml_plugin falls back to retry_get_plugin, the fallback attempts interface_obj.__class__.__base__(), which raises TypeError: Can't instantiate abstract class BaseYamlInterface with abstract method validator. This masks the real error and prevents any useful diagnostic from reaching the caller.

Background and Motivation

• BaseYamlInterface inherits from BaseInterface and has an abstract validator method. Calling __base__() on a concrete interface subclass therefore tries to instantiate BaseYamlInterface directly, which fails.
• This path is only hit when the happy path of get_yaml_plugin fails (e.g. plugin name not found in the registered file), so it is normally hidden behind successful lookups. It surfaced while developing tests for PR #17.

Code to demonstrate issue

• Trigger any path that causes get_yaml_plugin to fall through to retry_get_plugin for a yaml-based interface. For example, splice a fake registry entry whose name field in the on-disk YAML does not match the registry key, then call:

self.real_reg_validator.get_yaml_plugin(configs, "<mismatched-name>")

Expected: a helpful error indicating the plugin could not be found. Actual:

TypeError: Can't instantiate abstract class BaseYamlInterface with abstract method validator

raised from pluginify/plugin_registry.py:847 at the line base_interface_class = interface_obj.__class__.__base__().

Checklist for Completion

• Investigate the intent of the __base__() call in retry_get_plugin -- it appears to assume the base class is concrete, which is not true for yaml-based interfaces.
• Replace the abstract-class instantiation with a working construct (likely just use interface_obj itself, or look up the class without instantiating).
• Add a regression test that exercises the fallback path for a yaml-based interface.