feat: enrich info command inventory

[Genmin]

Summary

• replace the stub info payload with a machine-readable inventory of supported Arbitrum chains and contracts
• reflect subcommands from Clap so new Commands variants show up automatically
• add human output with chain and subcommand summaries
• add regression tests for the first supported chain and reflected subcommand coverage

Closes #5

Validation

• cargo fmt --check
• cargo test
• cargo clippy --all-targets -- -D warnings
• cargo run --quiet -- info | JSON parse + checks for chain_id 42161 and agent-deposit
• cargo run --quiet -- info --human