231 — One Migration Helper for Daemon Job Schemas

Legacy daemon databases are a compatibility surface, but compatibility code should not multiply every time a column is added. R14 (story 1194) consolidates six near-identical lazy migrations into one helper that reads daemon_jobs once and adds any missing columns from a caller-provided definition map.

The dispatch and reconciler paths now retain their existing column-specific context while sharing the same no-op behavior for absent tables, existing columns, and transient migration errors. The vestigial schema_version table was also retired after a repository-wide search found no reads or writes against it; unrelated JSON and YAML schema_version metadata remains unchanged.

The result is a smaller migration surface that is easier to extend without creating another ad-hoc helper.