0544 — Dead-field pass: two deletions, one exemption

Context

The config-refinement item’s last sweep: every config/options field, vocabulary read-model field, and datastore row-struct field audited for a production reader; staticcheck (U1000) and unparam run over all three code modules for dead vars/params. The codebase came back almost clean.

Decision

Deleted, per the no-fields-without-readers rule:

• WorkerSnapshot.OldestInstanceAge and its whole chain (adapter line, WorkerSnapshotData.OldestInstanceAgeSecs, the oldest_instance_age_secs SQL expression). It was added for the worker state gauges, but the metrics collector shipped deriving MetricOldestUnclaimedAge from UnclaimedFor instead — nothing ever read it. worker_instance.created_at stays: audit bookkeeping, like every other table’s created_at.
• WorkerInstanceData.ExpiresAt: scanned from ClaimInstance’s RETURNING, never adapted — the vocabulary WorkerInstance never carried it (renew and release match on token, not on the expiry value).

Exempted: JobRequest.CronJobId has no in-library reader, but JobRequest is the job_requests topic’s WIRE PAYLOAD, not a read-model — its reader is user consumer code, and the id is the only stable way to correlate a request to its cron_job row (a destroyed job’s name is reusable). Payload contract fields are judged by the wire contract, not the read-model rule.

Consequences

• WorkerSnapshot is one field slimmer pre-v1; re-adding an instance-age gauge later starts from worker_instance.created_at, which survives.
• staticcheck/unparam found nothing else across root, cmd/vulkan, and otelvulkan — the earlier 14b tier reviews left no other dead surface.