0341 — Schema lives as versioned Go code; golang-migrate and its .sql files are deleted

Context. Schema bootstrap and evolution had lived in golang-migrate .sql files applied by justfile recipes, outside the library’s own API — nothing in code could register a topic’s tables or advance a schema version. Dated approximately; built across July 2026.

Decision. pkg/migrate runs schema changes as versioned Go migrations through a runner: RunOnce migrates one entity, RunAll loops every topic and continues past a per-topic failure, joining errors with errors.Join. migrations/*.sql, migrations/old/, and the justfile migrate-up/migrate-down recipes were removed; RegisterSystem’s idempotent CREATE-IF-NOT-EXISTS baseline is the bootstrap path.

Consequences. Schema is applied through the same guarded API surface as everything else, per-topic table families can be migrated per topic, and a partial multi-topic failure reports every topic’s error instead of stopping at the first. There is no .sql file trail to keep in sync with code.