Deploy attempt 2: prefer-ipv6 fixed, two new defects, model partially populated ...

The prefer-ipv6 failure did NOT recur. Two new ones did, and for the first time
the model is not empty: MEASURED 23 applications, 0 machines, 0 units.
Attempt 1 aborted during VALIDATION; this one reached EXECUTION, which is why
it left residue. NOTHING IS PROVISIONED -- no MAAS machine left Ready, no disk
written.

DEFECT 1: the rack's ~/repo-stage is a PARTIAL COPY of the repo with no
policies/, and bundle.yaml:214 is the only local-file reference in the deploy
input. juju resolves it relative to the bundle, so it must exist ON THE HOST
THAT DEPLOYS. Nothing caught it: --dry-run does not upload resources (the
SECOND --dry-run blind spot in two days), attempt 1 aborted before resource
upload, and preflight runs on voffice1 where policies/ DOES exist -- the same
wrong-host instrument class already recorded twice, and the second instance
this session. Fixed forward, both files sha256-verified.

DEFECT 2: a bundle relying on default-base is deployable exactly ONCE. The
re-run failed on barbican 265-vs-261. Measured: 265 is the ubuntu@22.04
revision, 261 the ubuntu@24.04 one. The 23 existing apps are all 22.04, so run
2a honoured bundle.yaml:85 -- but on a re-run, for an app that ALREADY EXISTS,
juju resolves without that default. A model-level default-base has NO EFFECT
(tested, then RESET). An explicit per-application base WORKS (tested read-only
on a throwaway; the error moved to the next app).

OWNED: two of those read-only tests were staged under /tmp and failed with
"no charm was found" -- the juju snap's PRIVATE /tmp, a trap this repo has
already recorded in CURRENT-STATE and the phase-4 runbook.

The rollback decision tree is written for tofu apply and defaults to
fix-forward, which is measured not to work here. A partial juju deploy is a
failure mode the repo does not cover. Recovery is an operator decision;
options are enumerated in the capture and the model residue is untouched.

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