fix(loss-harness): drop the needless mut on send_wires — workspace clippy is -D warnings

Slipped through 421e8112: the on-box clippy runs covered punktfunk-core and
punktfunk-host but not the tools crates; CI's workspace-wide pass caught it.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tools/loss-harness/src/main.rs

@@ -46,7 +46,7 @@ fn run(
     let mut host = Session::new(config(Role::Host, scheme, drop_period), Box::new(h)).unwrap();
     let mut client = Session::new(config(Role::Client, scheme, drop_period), Box::new(c)).unwrap();
 
-    let mut send_wires = |host: &mut Session, wires: Vec<Vec<u8>>| {
+    let send_wires = |host: &mut Session, wires: Vec<Vec<u8>>| {
         let refs: Vec<&[u8]> = wires.iter().map(|w| w.as_slice()).collect();
         host.send_sealed(&refs).unwrap();
         drop(refs);