Function tool_result_key 

pub fn tool_result_key(content: &[u8]) -> Key

Content-addressed identity of a tool result. The MCP tool layer registers a node under this key carrying the file roots the result depended on, and the proxy records the same key as an upstream edge of any LLM call whose prompt embedded that result, so editing one of those files cascades file -> this node -> the dependent completions. Both layers must hash identically, so the function lives here in the shared runtime crate.