NNTP shares: the account's connections shared by priority

The coordinator (38) and the prober (8) had a fixed split; with history
paused the coordinator's stood idle while the prober's were its limit.
nntp_shares: each process syncs every 15 s (priority, minimum, what it could
use, what it has open) and gets what it may open: minimums first, then by
priority what each wants, growing only into connections the others closed
or gave up. The pool's size and the prober's lanes follow the grant; the
coordinator doubles its want while work waits for a connection, else asks
for its peak in use and a margin; the prober wants its maximum unless the
queue is dry. Claims scale with the lanes.

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

deploy/compose.yaml

@@ -115,11 +115,14 @@ services:
       <<: *app-env
       NNTP_CONNECTIONS: ${NNTP_CONNECTIONS:-38}
 
-  # 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 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).
+  # Phase 2's prober: reads the probe queue's articles over connections of its
+  # own. The account has 50 (NNTP_ACCOUNT_CONNECTIONS): 5 reserved (the
+  # coordinator's plain one, 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), the other 45 shared
+  # by the coordinator (NNTP_MIN_CONNECTIONS–NNTP_CONNECTIONS) and the prober
+  # (PROBE_MIN_CONNECTIONS–PROBE_CONNECTIONS), headers first
+  # (app/services/nntp_shares.ts).
   prober:
     <<: *app
     command: ['node', 'ace', 'probe:run']