Python: Safely clone plugins

[moonbox3]

Motivation and Context

Currently, we attempt to deep copy plugins, no matter what the plugin instance holds. This will cause issues when plugins contain unpickleable items like an async generator.

Description

• Closes Python: Bug: Cannot register agent with MCP plugin due to async context manager in HandoffOrchestration #12819

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the SK Contribution Guidelines and the pre-submission formatting script raises no violations
• All unit tests pass, and I have added new tests where possible
• I didn't break anyone 😄

[moonbox3]

Python Test Coverage Report •

File	Stmts	Miss	Cover	Missing
kernel.py	234	58	75%	149, 160, 164, 320–321, 323, 405, 411–412, 416–417, 470–474, 476–477, 490–499, 501, 503–504, 506–526, 528–533
TOTAL	27120	4727	82%

Python Unit Test Overview

Tests	Skipped	Failures	Errors	Time
3720	22 💤	0 ❌	0 🔥	1m 42s ⏱️