feat(litellm): async retain, reflect support, and API cleanup #446

Job	Run time
build-docs	1m 36s
build-typescript-client	12s
test-rust-cli	1m 50s
test-rust-client	1m 27s
build-docker-images (api-only, api)	5m 33s
test-python-client	1m 15s
lint-helm-chart	6s
test-api	4m 22s
build-docker-images (standalone, standalone)	5m 55s
build-python-packages (hindsight-all, hindsight)	8s
verify-generated-files	3m 59s
test-integration	1m 10s
test-litellm-integration	16s
build-python-packages (hindsight-api, hindsight-api)	8s
build-control-plane	1m 17s
build-api-python-versions (3.12)	9s
build-python-packages (hindsight-client, hindsight-clients/python)	12s
build-api-python-versions (3.13)	10s
build-docker-images (cp-only, control-plane)	4m 2s
build-python-packages (hindsight-embed, hindsight-embed)	9s
test-typescript-client	1m 26s
test-embed	1m 7s
build-api-python-versions (3.11)	8s
test-doc-examples	3m 37s
	40m 14s

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