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/src/adapters/in-memory-decision-case-repository.ts

@@ -0,0 +1,47 @@
+/**
+ * In-Memory DecisionCase Repository
+ *
+ * Adapter: Implements DecisionCaseRepository using a Map.
+ * Purpose: Testing, development, CI/CD pipelines.
+ * NOT for production.
+ */
+
+import {
+  DecisionCase,
+  DecisionCaseId,
+  ArtifactId,
+  EvidenceId,
+} from '@landvex/domain';
+import { DecisionCaseRepository } from '../repositories/repository-interfaces';
+
+export class InMemoryDecisionCaseRepository implements DecisionCaseRepository {
+  private cases = new Map<string, DecisionCase>();
+
+  async save(decisionCase: DecisionCase): Promise<void> {
+    this.cases.set(decisionCase.id, decisionCase);
+  }
+
+  async findById(id: DecisionCaseId): Promise<DecisionCase | null> {
+    return this.cases.get(id) ?? null;
+  }
+
+  async findByArtifact(artifactId: ArtifactId): Promise<DecisionCase[]> {
+    return Array.from(this.cases.values())
+      .filter(c => c.evidenceIds.includes(artifactId as any));
+  }
+
+  async findByStatus(
+    status: 'pending' | 'under_review' | 'approved' | 'rejected'
+  ): Promise<DecisionCase[]> {
+    return Array.from(this.cases.values())
+      .filter(c => c.status === status);
+  }
+
+  clear(): void {
+    this.cases.clear();
+  }
+
+  count(): number {
+    return this.cases.size;
+  }
+}