Refactor Hamilton workspace tests into infrastructure tree

[2-Coatl]

Summary

• relocate the Hamilton LLM example tests under infrastructure/workspace/tests/hamilton_llm and add a workspace-level registry test
• expose the new test directory through infrastructure.workspace.TEST_SUITES while exporting hamilton_llm via __all__
• refresh Hamilton documentation and the ExecPlan to reference the new workspace test location

Testing

• python3 -m pytest infrastructure/workspace/tests
• python3 -m pytest docs/qa/testing/test_documentation_alignment.py::test_hamilton_framework_integration_doc_is_published

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Codex Task