PR-002: Persistence Adapters — in-memory, zero external dependencies

- Repository interfaces defined by domain (@landvex/domain)
- 6 in-memory adapters: Session, Mission, DecisionCase, Artifact, EventStore, UnitOfWork
- 9 tests verifying adapter contracts
- Domain unchanged — infrastructure depends on domain, never reverse
- ADR-006: In-Memory Adapters for Testing

Definition of Done met:
- All adapters compile against domain interfaces
- Unit tests pass (9/9)
- No PostgreSQL, S3, Express, AI in this PR
- Ready for PR-003: PostgreSQL adapters

packages/infrastructure/adr/ADR-006-In-Memory-Adapters-for-Testing.md

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+# ADR-006: In-Memory Adapters for Testing
+
+## Status
+Accepted
+
+## Context
+The domain model needs to be tested without external dependencies (PostgreSQL, S3, etc.). We need fast, isolated tests that verify domain behavior.
+
+## Decision
+Implement in-memory adapters for all repository interfaces:
+- InMemoryFieldSessionRepository
+- InMemoryMissionRepository
+- InMemoryDecisionCaseRepository
+- InMemoryArtifactRegistry
+- InMemoryEventStore
+- InMemoryUnitOfWork
+
+These adapters:
+- Implement the same interfaces as production adapters
+- Store data in memory (Map, Array)
+- Can be reset between tests
+- Are never used in production
+
+## Consequences
+
+### Positive
+- Tests run in milliseconds
+- No database setup required
+- Parallel test execution safe
+- Documents how repositories are used
+
+### Negative
+- Not production-realistic (no transactions, no persistence)
+- Need separate integration tests for production adapters
+
+## Related
+- ADR-001: Domain knows nothing about AI
+- ADR-002: Artifact is common base contract
+- ADR-003: Event Sourcing for traceability