compress_tool_result for the /v1/compress gateway contract (#702):
identical compression, but a lossy result advertises its retrieval hash in
LiteLLM’s regex-locked hash=<24hex> form, so a gateway running the
headroom-guardrail CCR loop (BerriAI/litellm#31681) can inject its retrieve
tool and resolve the original via GET /v1/retrieve/{hash}.