* test: move key-gated tests/test_litellm SDK tests into tests/llm_translation and drop empty folders
* test: make token counter and health check unit tests run offline
* ci: point unit shards, rust path filter, Makefile and docs at tests/unit
* docs: fix stale test_litellm run paths in moved llm_translation tests
* fix: correct databricks e2e sys.path depth and contributing example path
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Co-authored-by: yuneng <yuneng@berri.ai>
Co-authored-by: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>