Rebuild: phase 2's prober reads the probe queue

probe:run (compose service prober, PROBE_CONNECTIONS, default 6) claims
waiting candidates of settled releases (lone, then par2, then archive),
fetches each article with BODY over connections of its own (no
compression) and inspects it: the yEnc name and size, the content type
from the first bytes, a par2 set's files, a RAR volume's entries and
whether they're encrypted. Results per release and kind in
release_inspections (CHUNK_TABLESPACE, the HDD); on the release
passworded, inner_name (the largest content name) and inspected_at.
430 = missing, not yEnc = error, both final; connection trouble puts
the candidate back.

Fetch and parse in one process: an article takes ~0.1 s per connection,
parsing a few ms (no queue in between). Parsers from voyager 1 (lib/yenc,
lib/rar, lib/par2, lib/content sniff) with their tests; XoverClient.body;
yencode.

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

deploy/compose.yaml

@@ -82,6 +82,16 @@ services:
       <<: *app-env
       NNTP_CONNECTIONS: ${NNTP_CONNECTIONS:-40}
 
+  # Phase 2's prober: reads the probe queue's articles over PROBE_CONNECTIONS
+  # connections of its own (next to the coordinator's 40 + 1; the account has 50).
+  prober:
+    <<: *app
+    command: ['node', 'ace', 'probe:run']
+    volumes: []
+    environment:
+      <<: *app-env
+      PROBE_CONNECTIONS: ${PROBE_CONNECTIONS:-6}
+
   # The Rust worker; it has no NNTP account and talks to web only. Stopped
   # before web (a worker holding a stream keeps the server from exiting).
   edge: