test(catalog): refresh the pinned catalog snapshot

[onel]

testdata/snapshot.json is a pinned copy of the published catalog, and TestNoUnmodeledFields checks it key by key so a field the catalog serves can never be one this box silently drops. That only works while the copy is close to what is actually served, and it had drifted.

The shape did not change; the apps did. Top-level keys are identical, no app key disappeared, and the guard passes.

One key is new to the file: external_costs. wireApp has modelled it since it landed (wire.go:112), but no published app declared one until now, so the pinned fixture never exercised it. It does now, which is the part of this refresh that actually buys coverage rather than just currency.

That also dated the comment on TestExternalCostsSurviveTheDigest, which stated no published app declares a cost. Reworded rather than removed: the test still constructs its own snapshot, so the byte-fidelity and field-ordering proof does not depend on which apps happen to be published — it is just no longer the only thing covering the field.

go test ./internal/catalog/...   ok
gofmt -l internal/catalog/       clean

No production code changes.

[greptile-apps]

Confidence Score: 5/5

The PR appears safe to merge, with no concrete blocking or non-blocking defects identified.

The changes are limited to a refreshed test fixture and an explanatory comment, and the fixture remains aligned with the digest-covered catalog wire model.

Important Files Changed

Filename	Overview
internal/catalog/testdata/snapshot.json	Refreshes the catalog fixture and adds real-world coverage of the modeled external_costs wire field without introducing an identified schema or integrity defect.
internal/catalog/wire_test.go	Updates documentation around the existing constructed external-cost digest test; test behavior is unchanged.

_{Reviews (1): Last reviewed commit: "test(catalog): refresh the pinned catalo..." | Re-trigger Greptile}