Actually validate the ISO registry

[francoisferrand]

validate_registry was meant to abort the ISO build when an image referenced by zenkoversion.yaml is missing from the registry. It has never checked a single image.

.. walks sequence nodes too (spec.capabilities.lifecycleRules, locationTypes), and yq treats indexing one with a string key as a hard error rather than a miss:

Error: cannot index array with 'image' (strconv.ParseInt: parsing "image": invalid syntax)

yq evaluates the whole expression before emitting anything, so a single sequence anywhere in the file empties the entire output — position doesn't matter. It ran inside a process substitution, so set -e never fired, the loop body never ran, missing stayed 0, and every build printed "Registry validation passed: all images are present."

Restricting the traversal to mapping nodes yields the expected 34 references. The list is now read into a variable first, so a yq failure or an empty result aborts instead of silently validating nothing — the original shape hid the exit status twice over.

Also adds coverage under tests/scripts/, since nothing exercised this function: all-present passes, each missing image aborts, and unreadable/empty input aborts. Those cases all pass against the previous code, which is the point.

Verification

Against the real zenkoversion.yaml, with one image absent from a temp IMAGES_ROOT:

expression	result
before	missing=0 → passes, missing image undetected
after	missing=1 → aborts

New tests: 6 of 7 fail against the previous code, all 7 pass after. Full pytest tests/scripts/ green (18), also run under the CI-pinned yq 4.44.3 as well as the 4.53.6 on the runners.

Cross-checked that turning the check on doesn't expose latent breakage: all 34 referenced images are among the 37 the build copies, so CI stays green.

Based on development/2.14 — validate_registry doesn't exist on 2.11–2.13, so this is the earliest affected branch.

Issue: ZENKO-5358

[bert-e]

Hello francoisferrand,

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[francoisferrand]

/approve

[bert-e]

I have successfully merged the changeset of this pull request
into targetted development branches:

• ✔️ development/2.16

The following branches have NOT changed:

• development/2.10
• development/2.11
• development/2.12
• development/2.13
• development/2.14
• development/2.15
• development/2.5
• development/2.6
• development/2.7
• development/2.8
• development/2.9

This pull request did not target the following hotfix branch(es) so they
were left untouched:

• hotfix/2.13.5

Please check the status of the associated issue ZENKO-5358.

Goodbye francoisferrand.

The following options are set: approve