feat: add marketplace commands (buy, info)

[joystick-ctrl]

Summary

Add CLI commands for interacting with the Arcade marketplace, enabling users to purchase NFTs from listings without calldata ambiguity.

Commands Added

controller marketplace info

Query order validity and details before purchasing.

controller marketplace info \
  --order-id 42 \
  --collection 0x123...abc \
  --token-id 1 \
  --chain-id SN_MAIN

controller marketplace buy

Purchase an NFT from a marketplace listing.

controller marketplace buy \
  --order-id 42 \
  --collection 0x123...abc \
  --token-id 1 \
  --chain-id SN_MAIN \
  --wait

Implementation Details

• u256 encoding: Properly encodes token IDs as (low, high) felt pairs
• Policy validation: Checks session policies before executing
• Order validation: Calls get_validity before attempting purchase
• Pattern consistency: Follows the same patterns as starterpack commands

Files Changed

• src/commands/marketplace/mod.rs - Module with shared utilities
• src/commands/marketplace/info.rs - Order info query command
• src/commands/marketplace/buy.rs - Purchase command
• src/main.rs - CLI command registration
• docs/PRD-marketplace-commands.md - Full PRD with TDD specs

Testing

Includes unit tests for:

• u256 encoding (small values, large values, hex parsing)
• Calldata building
• Chain ID resolution

Related

• Based on Arcade marketplace contract: arcade/contracts/src/systems/marketplace.cairo
• Follows patterns from starterpack commands