Prober stops claiming under 6 GB free (was 12)

The NVMe floor is 4 GB since Oct 23; at 12 the prober had claimed nothing
since Oct 23 15:30 (7-10 GB free).

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

deploy/compose.yaml

@@ -130,9 +130,9 @@ services:
     environment:
       <<: *app-env
       PROBE_CONNECTIONS: ${PROBE_CONNECTIONS:-8}
-      # No claims under this much free on the NVMe (its overlay root): 2 GB above the 10 GB floor, for what the
-      # tail, the merger and the judge write meanwhile.
-      PROBE_MIN_FREE_GB: ${PROBE_MIN_FREE_GB:-12}
+      # No claims under this much free on the NVMe (its overlay root): 2 GB above the 4 GB floor (2026-10-24), for
+      # what the tail, the merger and the judge write meanwhile.
+      PROBE_MIN_FREE_GB: ${PROBE_MIN_FREE_GB:-6}
 
   # The par2 merge: releases whose files one par2 set describes (what the prober read) become one. No NNTP.
   merger: