Replace runtime argv handoff with a sealed typed record

crates/lazaret-runtime-supervisor/src/supervision/runtime.rs

@@ -598,12 +598,3 @@ fn receive_exact(descriptor: impl AsFd + Copy, mut bytes: &mut [u8]) -> io::Resu
     }
     Ok(())
 }
-
-fn hex(bytes: &[u8]) -> String {
-    use std::fmt::Write as _;
-
-    bytes.iter().fold(String::new(), |mut output, byte| {
-        write!(output, "{byte:02x}").expect("writing to a String cannot fail");
-        output
-    })
-}