shared: opt-in CIP-33 reference-scripts for script-spending txs

When ESCROW_REF_UTXO / ADVERT_REF_UTXO env vars are set (format
<txhash>#<idx>), Claim/Submit/Accept/Reclaim/RetireAdvert call
.readFrom([refUtxo]) instead of inlining the validator CBOR via
.attach.SpendingValidator(). Lucid-evolution 0.4.30 auto-extracts
utxo.scriptRef into the script-witness map (dist/index.js:1903–1913),
so no separate attach call is needed. Default (env unset) is unchanged.

Adds buildLiveTxForPublishReferenceScripts (a one-shot tx that
publishes both validators as scriptRef-bearing UTxOs at a caller-
supplied address — typically the all-zero-pkh enterprise burn address)
and the supplier tx:publish-reference-scripts CLI that wraps it.

Targeted at testnet trial; mainnet rollout is a separate flip after
verification.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

buyer/.env.example

@@ -26,6 +26,15 @@ BUYER_PORT=8070
 # See ARCHITECTURE.md §9 follow-up — naming drift to be reconciled.)
 NETWORK_ID=0
 
+# ─── Optional: CIP-33 reference scripts ───────────────────────────────────
+# When set, buyer-signed script-spending txs (Accept, Reclaim) read the
+# escrow validator from an on-chain reference UTxO instead of inlining
+# its CBOR — saving witness-set fees. Must match the values published
+# by `supplier tx:publish-reference-scripts` (printed to stdout by that
+# CLI). Leave unset to use inlined scripts (current behavior).
+# ESCROW_REF_UTXO=<txhash>#0
+# ADVERT_REF_UTXO=<txhash>#1   # not used by buyer; kept for env-file symmetry
+
 # ─── Reserved for M1-F ────────────────────────────────────────────────────
 # INDEXER_TIMEOUT_MS is referenced in deploy/README.md but is NOT yet read
 # by buyer/src/config.ts. M1-F should add it; see follow-ups.