Operator utterance, verbatim: "Sync the backports into the mirror".

Question as presented: 22 of 33 units failed their install hook on one measured
cause -- the mirror serves jammy/jammy-security/jammy-updates 200 and
jammy-backports 404, exactly dc-mirror.sh:179's "jammy triple" scope, while
every node's sources.list carries jammy-backports because the Step-3.5
apt-mirror model-config rewrites EVERY suite to the DC mirror. Options: (a) add
the suite and re-sync, (b) drop backports from the nodes' sources.

Recorded as a D-135 AMENDMENT. OPS under GA-R3, no new D-number; D-135's per-DC
strategy split (dc0 full mirror / dc1 caching proxy) is unchanged.

Cost measured BEFORE the ruling was put: ~1.00 GiB / 461 packages against a
951 GB mirror with 1.8 T free -- ~0.1%.

Recorded as owed, not built: dc-mirror.sh check verifies sync STATUS, not SUITE
COVERAGE against what the deployed image's sources.list requests, which is why
it read PASS throughout. Same class the mirror gate was already fixed for once.

Committed and pushed BEFORE the dependent work.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HvCyrwvYTTcDYnRErfMsNf