ludic.net: a message's record, bytes and lists kept - queued ones back to a pool once sent or taken, the inbox's two drains on, a read text interned

np_queue made a NetMsg and a buffer per message, every flush a new keep list, and every message
that came in a NetMessage and a buffer; nr_text a new string per text read. A party plays at
dozens a second, so all of it is kept now: a pool of MTU-sized records for the queue (a peer's two
lists swapped by the flush), the inbox's records in two halves swapped when a message finds the
inbox empty, net_written's one record, a relay hello's and a STUN request's bytes in one scratch
buffer, and the texts read out interned. Tests: 6000 messages with the heap flat (Os.heap_bytes),
and an inbox record that holds still across a drain and comes back two drains on.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

packages/ludic.net/stun.ludic

@@ -15,7 +15,7 @@ function net__stun_send(net_st: mut NetState) -> void {
     }
     if net_st.net__stun_ip == 0 { return }
   }
-  let b = buffer(20)
+  let b = net_st.net__sb
   nb_put8(b, 0, 0)          # a binding request, no attributes
   nb_put8(b, 1, 1)
   nb_put8(b, 2, 0)