feat(jpa): implement the JPA relational persistence platform

Implements the Stable and Experimental JPA persistence platform designs
against real PostgreSQL, adapted to this repository's fail-closed 19-leaf
registry.

The design models the platform as 25 Gradle projects. `src/settings.gradle`
throws unless the registry holds exactly 19 leaves, so the plan's modules
become packages inside `:adapter:outbound:persistence-jpa` (starter in
`:app-bootstrap`, testkit in its own source set). The full mapping, the
renames this repository's naming gate required, and every deliberate
substitution are recorded in `docs/jpa/repository-adaptation.md`.

Seven Docker-backed lanes replace the plan's seven JVM test suites. Each
fails closed: a lane that discovers nothing, or a container that cannot
start, is an error rather than a skip.

Three defects the contracts found against a real server:

- `CommitFailureClassifier` treated only SQLSTATE 40003, class 08, and
  transport breaks as completion-unknown. A backend terminated mid-commit
  reports 57P01, and the commit record may already be in the WAL — so a
  possibly-committed transaction could be re-run. 57P01/57P02/57P03 now
  classify as completion-unknown.
- `SchemaTenantMigrationOrchestrator` recorded `MigrateResult`'s target
  version, which is empty for a tenant already current, reporting migrated
  tenants as unmigrated during a partial rollout. It now reads the applied
  version back from the tenant's schema history.
- `JpaStreamExecutor` checked only the declared return type for reactive
  publishers, and `RegisteredPostgreSqlCopyLoader` passed the COPY timeout
  to `SET`, which is parsed before parameter binding.

`JpaModuleBoundaryTest` enforces the plan's module map as package rules;
`verifyCleanArchitectureDependencies` governs edges between leaves and
cannot see these. Its first assertion is that the import is non-empty,
because every rule under it is a `noClasses()` rule and would pass
vacuously on an empty import.

Verified: 128 container tests across all seven lanes, 1183 unit tests,
`:adapter:outbound:persistence-jpa:check`, `:app-bootstrap:check`,
`verifyCleanArchitectureDependencies`, `verifyOneTypePerFile`.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

docs/adr/ADR-JPA-003-completion-unknown.md

@@ -0,0 +1,41 @@
+# ADR-JPA-003 — Completion unknown is never retried
+
+- Status: Accepted
+- Date: 2026-08-11
+- Design: §17
+
+## Context
+
+A connection can break while a commit is in flight. The server may have committed; the
+acknowledgement may simply have been lost. The driver cannot tell the two apart.
+
+## Decision
+
+`TransactionCompletionUnknownException` is never retried, automatically or otherwise. It is
+produced only by a failure observed while the transaction phase is `COMMITTING`, and only for
+SQLSTATE `40003`, a connection-class (`08*`) state, or a transport break. Recovery is
+domain-specific reconciliation through `TransactionCompletionResolver`.
+
+## Consequences
+
+Retrying a possibly-committed write is the most damaging thing this platform could do: a duplicate
+payment, a duplicate order, a double decrement. There is no budget or backoff that makes it safe,
+because the failure is epistemic rather than transient.
+
+The invariant is enforced at the type level rather than by policy alone. `JpaFailureContext` refuses
+to construct a retryable completion-unknown context, and the exception rebuilds its context through
+the safe factory whatever it is handed. A future policy bug therefore cannot produce an unsafe
+retry — the value it would need does not exist.
+
+The rule is deliberately narrow in the other direction too. Classifying every connection failure as
+completion-unknown would push ordinary pool exhaustion and server restarts into the reconciliation
+queue, which trains operators to clear that queue without reading it — and then the one entry that
+mattered gets cleared with the rest.
+
+The cost is that the domain must supply the resolver. The platform cannot: only the domain knows
+which idempotency record, business row, or outbox entry proves the write happened.
+
+## Enforcement
+
+`JpaFailureContextTest`; `DefaultJpaRetryPolicyTest`; `CommitFailureClassifierTest`; release gate
+`completion-unknown-no-retry`.