Document a third accepted Prisma DDL exception (storage engine)

Task 3 found Prisma's generated migration SQL never emits an
explicit ENGINE=... clause, same root cause as the already-accepted
collation exception (no schema-level attribute exists). No practical
impact: the baseline never executes this SQL against the real DB,
and any fresh deploy still gets InnoDB from the server default.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

docs/superpowers/plans/2026-07-31-prisma-orm-migrations.md

@@ -10,7 +10,7 @@
 
 ## Global Constraints
 
-- `prisma/schema.prisma` must reproduce `db/schema.sql` column-for-column, so the initial migration is a no-op against databases that already have the table (spec: "Schema"). Two documented, accepted exceptions where Prisma's MySQL provider has no schema-level equivalent (verified empirically against the real DB's `SHOW CREATE TABLE conversion_jobs`, and confirmed acceptable by the user on 2026-07-31): (1) table collation — the live MariaDB server defaults to `utf8mb4_uca1400_ai_ci` (a MariaDB-specific collation), but Prisma always emits `utf8mb4_unicode_ci` in generated DDL with no schema attribute to override it; (2) `updatedAt`'s `ON UPDATE CURRENT_TIMESTAMP` — Prisma's `@updatedAt` is implemented client-side only for the `mysql` provider and never emits a DB-level `ON UPDATE` clause. Neither has practical impact here: the baseline (Task 3) marks the initial migration applied without ever executing its SQL against the real database, and every write to `conversion_jobs` after this migration goes through Prisma Client, which sets `updatedAt` itself. All other columns (types, defaults, index/constraint names) must match exactly — see Task 1's schema, which uses `@db.DateTime(0)` and explicit `map:` names for this reason.
+- `prisma/schema.prisma` must reproduce `db/schema.sql` column-for-column, so the initial migration is a no-op against databases that already have the table (spec: "Schema"). Three documented, accepted exceptions where Prisma's MySQL provider has no schema-level equivalent (verified empirically against the real DB's `SHOW CREATE TABLE conversion_jobs`, and confirmed acceptable by the user on 2026-07-31): (1) table collation — the live MariaDB server defaults to `utf8mb4_uca1400_ai_ci` (a MariaDB-specific collation), but Prisma always emits `utf8mb4_unicode_ci` in generated DDL with no schema attribute to override it; (2) `updatedAt`'s `ON UPDATE CURRENT_TIMESTAMP` — Prisma's `@updatedAt` is implemented client-side only for the `mysql` provider and never emits a DB-level `ON UPDATE` clause; (3) storage engine — Prisma's generated DDL never emits an explicit `ENGINE=...` clause (no schema-level attribute controls it), relying on the server default, which is InnoDB on effectively every real MySQL/MariaDB install including this project's (confirmed during Task 3 execution on 2026-07-31, same root cause as (1): no schema-level attribute exists). None of the three have practical impact here: the baseline (Task 3) marks the initial migration applied without ever executing its SQL against the real database, and every write to `conversion_jobs` after this migration goes through Prisma Client, which sets `updatedAt` itself; a fresh environment created via `prisma migrate deploy` would still get InnoDB from the server default. All other columns (types, defaults, index/constraint names) must match exactly — see Task 1's schema, which uses `@db.DateTime(0)` and explicit `map:` names for this reason.
 - `DATABASE_URL` is never written into `.env` or `.env.local` — it is always computed on demand from the existing `DB_HOST`/`DB_USER`/`DB_PASSWORD`/`DB_NAME` variables (spec: "Running Prisma CLI locally"). `.env` holds production credentials and must never be loaded for local work (CLAUDE.md).
 - The connection string includes `?connection_limit=10`, preserving the current pool's `connectionLimit: 10` (spec: "Running Prisma CLI locally").
 - `getJobByUuid`, `findPendingJobs`, and `findExpiredJobs` must never expose `errorLog` — only `getJobErrorLog` does (spec: "Data access layer").