Flyway migration generation regressed: ADR-0015 removed the meta:migrate --flyway mojo and the shared-engine Flyway output adapter was never built #192

Summary

metaobjects once shipped Flyway-named migration generation for JVM consumers (the Java meta:migrate --flyway Maven mojo, plugin v7.0.0). ADR-0015 consolidated all migration onto the shared TS engine and removed that mojo, designating a "Flyway-prefix output adapter" on the shared engine as its replacement — but that adapter was never built.

Net effect: a Spring-Boot-Kotlin + Exposed + Flyway consumer today has no supported path to generate migrations from metadata. Yet the generated meta init agent-context (.metaobjects/AGENTS.md) still instructs adopters to "never hand-write SQL … apply schema only through meta migrate" — advice that is impossible to follow on a Flyway stack, because there is no meta migrate output that Flyway can consume. This misdirects adopters (human and agent) and forces hand-authored V<n>__*.sql that only a boot-time drift-gate keeps honest.

How it regressed

• The Java maven-plugin MetaDataMigrateMojo gained a Flyway-naming option in 4ca10dd2 ("feat(maven-plugin): meta:migrate Flyway-naming option for codegen-kotlin consumers"), shipped in Java plugin 7.0.0 (its plugin.xml lists a migrate goal). Design of record: docs/superpowers/specs/2026-05-25-codegen-kotlin-design.md §5.1 — <flyway>true</flyway> → scan flywayDir for the highest V<N>__, increment, emit V<N+1>__<slug>.sql.
• 77a5c46a ("refactor(omdb)!: remove meta:migrate goal + Java migration-conformance scenarios") removed the mojo and the Java migrate engine behind it, per ADR-0015 (single shared migrate engine). ADR-0015 §3 explicitly designates Flyway-prefix (V__/U__) as reference output adapter fix(cli): scaffold outDir defaults to src/generated, not ./src/db #1 and notes the prior Flyway-emit groundwork "should inform the shared adapter."
• That adapter was never implemented: server/typescript/packages/migrate-ts/src has zero flyway references. meta migrate emits only its own <seq>-<slug>/up.sql + down.sql layout plus a private ledger table — incompatible with a Flyway flyway_schema_history boot without an adapter.

Impact on JVM/Flyway consumers

1. No migration-generation path. The current Java maven-plugin (e.g. 7.7.8) exposes goals generate, verify, docs, editor, help — no migrate. The TS CLI's output layout can't feed Flyway. So metadata → Flyway migration must be hand-authored to match codegen — the exact thing the doctrine says never to do.
2. The generated scaffold actively misdirects. meta init emits .metaobjects/AGENTS.md with "never hand-write SQL … apply schema only through meta migrate." On a Flyway stack there is no such command, so an agent/dev following the scaffold hunts for tooling that does not exist. (This recently cost a real multi-file investigation for one such consumer before the removal history was uncovered.)

Proposed fix

1. Build the ADR-0015 Flyway-prefix output adapter on the shared TS migrate engine (already the accepted plan-of-record; the removed nextFlywayVersion scanner from 4ca10dd2 is prior art). Emit V<N+1>__<slug>.sql into a configurable flywayDir, diffing the offline snapshot (meta migrate baseline --from-db seeds it once). Prove emitted-DDL fidelity against the codegen-kotlin Exposed table shapes via meta verify --db. Note the known gaps the engine does not yet model (triggers, cross-column CHECKs, function-valued defaults, GIN array indexes) will still require some hand-authored SQL — the adapter should degrade gracefully, not silently drop them.
2. Until it ships, correct the meta init scaffold so a Flyway-configured consumer's generated .metaobjects/AGENTS.md does not claim meta migrate is the schema-apply path. For a Flyway stack it should state that migrations are hand-authored to match codegen and enforced by the boot-time table/DB drift-gate (meta verify --db) — or at minimum not assert a command that isn't shipped for that stack.

Evidence (all in this repo)

• ADR: spec/decisions/ADR-0015-single-shared-migrate-engine.md (§3 output-adapter design; Flyway-prefix reference; build path pending)
• Removed mojo: git show 4ca10dd2 (added Flyway option) / git show 77a5c46a (removed the goal)
• Superseded design: docs/superpowers/specs/2026-05-25-codegen-kotlin-design.md §5.1
• The gap: no flyway references anywhere under server/typescript/packages/migrate-ts/src