feat(x402): Integrated payai facilitator

.env-example

@@ -34,16 +34,24 @@ export X402_PRICE_USDC=0.1
 # Use 'eip155:84532' for Base Sepolia (testnet)
 export x402_NETWORK=eip155:8453
 
-# Primary Facilitator
-# Options: 'cdp' (Coinbase) or 'dexter' (Dexter.cash - no API keys required)
-export PRIMARY_FACILITATOR=cdp
+# Primary Facilitator (used when ACTIVE_FACILITATORS is unset — single-facilitator mode)
+# Options: 'cdp' (Coinbase), 'dexter' (Dexter.cash), or 'payai' (PayAI)
+export PRIMARY_FACILITATOR=dexter
 
-# Facilitator URLs
-# For Coinbase CDP (recommended): https://api.cdp.coinbase.com/platform/v2/x402
-# For Dexter (no API keys):https://x402.dexter.cash
-# URL are not used when PRIMARY_FACILITATOR is set
+# Multi-facilitator (x402 v2): comma-separated *additional* facilitators; PRIMARY_FACILITATOR is always first (precedence).
+# x402_FACILITATOR_URL applies only in single-facilitator mode.
+# export ACTIVE_FACILITATORS=dexter,payai
+
+# Bazaar discovery extension on 402 payment requirements (default on). Set false to omit.
+# export X402_BAZAAR_ENABLED=true
+
+# Facilitator URL override (optional). If set, this URL is used regardless of PRIMARY_FACILITATOR.
+# Otherwise the URL is chosen from PRIMARY_FACILITATOR (built-in defaults per provider).
 # export x402_FACILITATOR_URL=https://api.cdp.coinbase.com/platform/v2/x402
 
+# PayAI only: optional custom facilitator host (default https://facilitator.payai.network)
+# export PAYAI_FACILITATOR_URL=https://facilitator.payai.network
+
 # CDP API Credentials (required when using CDP facilitator)
 # Get these from https://cdp.coinbase.com - API Keys section
 # Not required for Dexter facilitator