feat(POS-008): completed feature

work/artifacts/POS-008/implementer.md

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+# POS-008 — Implementer evidence
+
+## What
+POST /pos/sales idempotent sale endpoint. tsc 0, verify verde.
+
+## Files
+- `src/modules/pos/domain/pos-sale.ts` — PosSaleInput, PosSaleResult, PosPaymentInput, PosPaymentResult types
+- `src/modules/pos/application/create-pos-sale.ts` — CreatePosSaleUseCase with transaction (BEGIN/COMMIT/ROLLBACK), idempotency check, cash session lock
+- `src/modules/pos/api/pos.routes.ts` — POST /pos/sales route with schema validation
+
+## Verification
+- `npm run build` → 0 TypeScript errors.
+- `./scripts/verify.sh` → green.
+
+## AC traceability
+| AC | Estado |
+|----|--------|
+| AC1 idempotent | ✅ idempotencyKey check returns existing |
+| AC2 atomic | ✅ BEGIN/COMMIT/ROLLBACK transaction |
+| AC3 items + payments | ✅ INSERT + total validation |
+| AC4 cash session update | ✅ UPDATE expected_cash_cents |
+| AC5 tsc/verify | ✅ |