PROBE_CONNECTIONS 8: 2 connections to spare

At 50 exactly the coordinator still got 502s now and then: a hedged request
closes its connection and opens another while the old one still counts.

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

deploy/compose.yaml

@@ -105,7 +105,8 @@ services:
 
   # Phase 2's prober: reads the probe queue's articles over PROBE_CONNECTIONS
   # connections of its own. The account has 50: the coordinator's 38 (+ its
-  # plain one), the prober's 9, the spotter's and the spot inspector's 1 each
+  # plain one), the prober's 8, the spotter's and the spot inspector's 1 each,
+  # 2 to spare (a hedged request closes its connection and opens another)
   # (with 10 the spot inspector got 502 Too many connections).
   prober:
     <<: *app
@@ -113,7 +114,7 @@ services:
     volumes: []
     environment:
       <<: *app-env
-      PROBE_CONNECTIONS: ${PROBE_CONNECTIONS:-9}
+      PROBE_CONNECTIONS: ${PROBE_CONNECTIONS:-8}
 
   # The par2 merge: releases whose files one par2 set describes (what the prober read) become one. No NNTP.
   merger: