feat(mcp): add timestamp to retain #506

Job	Run time
lint-helm-chart	7s
build-control-plane	1m 2s
test-rust-cli	2m 28s
build-docs	1m 45s
build-typescript-client	14s
build-docker-images (cp-only, control-plane)	3m 50s
build-docker-images (standalone, standalone)	7m 0s
build-docker-images (api-only, api)	7m 20s
test-integration	1m 31s
test-rust-client	2m 11s
verify-generated-files	4m 18s
test-python-client	1m 45s
build-api-python-versions (3.11)	9s
build-python-packages (hindsight-api, hindsight-api)	12s
test-embed	1m 17s
test-api	4m 47s
test-litellm-integration	17s
build-api-python-versions (3.13)	11s
build-python-packages (hindsight-embed, hindsight-embed)	7s
test-typescript-client	1m 31s
build-python-packages (hindsight-all, hindsight)	8s
build-api-python-versions (3.12)	13s
build-python-packages (hindsight-client, hindsight-clients/python)	8s
test-doc-examples	4m 23s
	46m 54s

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