erlang: send_after to registered name + gen_server timeout returns (T5+T6, 771/771)

T5 — send_after addresses a registered atom name; the delayed message
lands in that process's mailbox (destination resolved at fire time,
dead/unregistered targets drop silently).

T6 — gen_server loop now handles the {reply,R,S,T} / {noreply,S,T}
timeout-bearing callback returns by scheduling {timeout} to itself via
send_after; handle_info({timeout}, S) fires when no other message
arrives first. Sanity-checks the library hookup.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lib/erlang/scoreboard.json

@@ -1,7 +1,7 @@
 {
   "language": "erlang",
-  "total_pass": 769,
-  "total": 769,
+  "total_pass": 771,
+  "total": 771,
   "suites": [
     {"name":"tokenize","pass":62,"total":62,"status":"ok"},
     {"name":"parse","pass":52,"total":52,"status":"ok"},
@@ -14,6 +14,6 @@
     {"name":"fib","pass":8,"total":8,"status":"ok"},
     {"name":"ffi","pass":37,"total":37,"status":"ok"},
     {"name":"vm","pass":78,"total":78,"status":"ok"},
-    {"name":"send_after","pass":8,"total":8,"status":"ok"}
+    {"name":"send_after","pass":10,"total":10,"status":"ok"}
   ]
 }