Multi-token support per pod #192

Summary

Support multiple tokens per pod, each with its own ticker and rate. The token trail layer (token.js) is already multi-token capable — trails are stored per-ticker at .well-known/token/<ticker>.json and transferToken() is parameterized by ticker.

Levels of ambition

Level 1: Multi-token config (~50 LOC)

• New flag: --pay-tokens "PODS:10,ACCESS:5,VIP:100" (ticker:rate pairs)
• .buy requires { ticker, amount } instead of defaulting to single token
• .info returns array of available tokens with rates
• .sell/.swap already carry ticker per offer — no change needed
• Backward compatible: --pay-token PODS --pay-rate 10 still works as single-token shorthand

Level 2: Token-gated resources (~100 LOC)

• Gate specific paths by token instead of sats: /pay/premium/* costs 1 VIP token
• Config: --pay-gate "/pay/premium:VIP:1,/pay/data:ACCESS:1"
• Middleware deducts from token trail instead of webledger for gated paths
• Useful for agents needing different capabilities at different token costs

Level 3: Token-to-token swaps (~150 LOC)

• Sell orders become two-sided: sell token X for token Y (or sats)
• Swap executes two trail transfers atomically
• Emergent price discovery between pod tokens

Design considerations

• Discovery: .info returns all tokens — agents can self-discover pricing
• Cross-pod portability: MRC20 proofs are already portable (withdraw on pod A, deposit on pod B)
• Token as reputation: Pods could check holdings from other pods before granting access
• Minting permissions: Currently owner-only via CLI — consider whether users can create tokens