docs(bolt12): note the nwc#2 ecosystem status (LND service exists, BOLT12 gap)

benthecarman/nostr-wallet-connect-lnd implements NWC-321 pay/receive (confirming
Phase 0), but is LND-backed so it rejects BOLT12 lno and returns no payer_proof.
The blocker for real BOLT12-zap testing is a CLN/LDK-backed NWC-321 service.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SpgpWLKzgD7vS9Fs4CXTR3

amethyst/plans/2026-07-24-nwc-bolt12-pay.md

@@ -3,6 +3,20 @@
 Status: **scoping** — no code yet. Depends on NIP-2421 (this branch) and the
 unmerged `nostr-wallet-connect/nwc#2` (adds `pay`/`receive` to NIP-47).
 
+## Ecosystem status (2026-07-25) — the wallet gap for real testing
+
+A real NWC-321 (`pay`/`receive`) service exists —
+[benthecarman/nostr-wallet-connect-lnd](https://github.com/benthecarman/nostr-wallet-connect-lnd)
+— which confirms the protocol we built (Phase 0) is real and adopted. **But it is
+LND-backed:** its `pay` "selects and pays a BOLT11 `lightning` instruction from a
+BIP-321 URI" and "BOLT12 `lno` instructions are not supported by this LND backend."
+So it returns no BOLT12 invoice and no `payer_proof`, and can't drive the NIP-2421
+zap loop. The blocker is the **node backend**, not the protocol: a CLN- or
+LDK-backed NWC-321 service (CLN has full BOLT12 and leads the payer-proof draft
+bolts#1346) would support `lno` + return `payer_proof`. Until one exists, the
+self-consistent interop harness (`cli/tests/bolt12/`, TODO) is the only way to
+exercise the full send → verify → count loop.
+
 ## What nwc#2 adds
 
 Two generalized methods replace the bolt11-only `pay_invoice`: