feat: add governed payment request slice

README.md

@@ -1,5 +1,26 @@
-# govoplan-payments
+# GovOPlaN Payments
 
 <!-- govoplan-repository-type:start -->
 **Repository type:** module (domain).
 <!-- govoplan-repository-type:end -->
+
+`govoplan-payments` owns replay-safe payment obligations, human payment
+references, append-only lifecycle evidence, and settlement reconciliation.
+
+The first vertical slice implements full manual/offline payment receipt. A
+Case, Workflow, or other procedure calls the Core `payments.requests`
+capability, retains the returned payment ID, and later supplies the exact
+amount/currency, external transaction reference, and a same-tenant versioned or
+checksum-bound evidence reference. Payments rejects changed replays, partial or
+cross-currency matches, cross-tenant evidence, and a second settlement.
+
+Online payment providers, applicant checkout, partial payments, refunds,
+reversals, Ledger posting, and XRechnung are intentionally separate next
+slices. See [docs/PAYMENTS_DOMAIN.md](docs/PAYMENTS_DOMAIN.md).
+
+Focused verification:
+
+```sh
+PYTHONPATH=src:/mnt/DATA/git/govoplan-core/src \
+  /mnt/DATA/git/govoplan/.venv/bin/python -m unittest discover -s tests
+```