Function standard_hook_env 

pub fn standard_hook_env(
    payload: &HookPayload,
    payload_path: &str,
) -> Result<Vec<(String, String)>, String>

Build the standard env vars every bash hook receives — the canonical EVERRUNS_HOOK_PAYLOAD_JSON plus the convenience scalars documented in specs/user-hooks.md. Returns the env in declaration order so dispatcher logs render deterministically.