feat: agent-deposit command + GitHub Actions CI

[abhicris]

What

Adds a first-class agent-deposit subcommand wrapping the Create Protocol AgentDeposit contract on Arbitrum, plus a GitHub Actions CI pipeline (fmt / check / clippy / test) since none existed.

# Read agent balance (USDC raw + decimal, chain resolved automatically)
arbitrum-cli agent-deposit 0xC750... --action balance

# Check Phase 1 registry membership
arbitrum-cli agent-deposit 0xC750... --action registered

# Prepare unsigned calldata for deposit / withdraw. The CLI is strictly
# key-less — agents sign via kcolbchain switchboard (or any wallet) and
# broadcast via `exec eth_sendRawTransaction`.
arbitrum-cli agent-deposit 0xC750... --action deposit  --amount 1000000
arbitrum-cli agent-deposit 0xC750... --action withdraw --amount 500000

# Override the contract for forks / staging deploys
arbitrum-cli agent-deposit 0xC750... --action balance --contract 0xabc...

Why

Create Protocol Phase 1 is an AI agent economy on Arbitrum: agents register, deposit USDC, execute tasks, earn fees. arbitrum-cli is positioned as the tool an LLM uses to drive the chain — an AgentDeposit verb closes the loop on the agent's own balance sheet without the agent having to hand-roll selectors or ABI calls.

Design choices worth flagging:

• Chain-to-address resolver (agent_deposit_address) — placeholder addresses today, one-line swap when the Arbitrum One redeployment of AgentDeposit lands. No scattered constants.
• Key-less by default — writes return unsigned calldata + metadata, not signed txs. The CLI never touches keys; callers compose with eth_sendRawTransaction.
• USDC decimals stay honest — amounts go in as raw units (1 USDC = 1_000_000). No implicit scaling on the write path; reads emit both balance_raw and balance_usdc.
• Chain id in the response — every response includes the chain it actually talked to, so an agent can't silently confuse testnet and mainnet.

CI

None existed before. Added .github/workflows/ci.yml covering:

• cargo fmt --check
• cargo check --all-targets
• cargo clippy --all-targets -- -D warnings
• cargo test --all-targets

With registry + build caching.

Tests

11 new unit tests in src/agent_deposit.rs covering:

• balanceOf / isRegistered / deposit / withdraw calldata encoding
• Action string parsing (balance | deposit | withdraw | registered, plus case + alias handling)
• Bad-input rejection (short address, non-hex)
• uint256 result decoding
• Chain-id → contract-address resolution
• Response JSON shape for both balance reads and unsigned-tx writes

All green locally (cargo test: 11 passed / 0 failed), clippy clean, fmt clean.

Manual verification

$ cargo run -- --rpc https://arb1.arbitrum.io/rpc \
    agent-deposit 0xC750...9664 --action deposit --amount 1000000 \
    --contract 0xdead...beef
{"action":"deposit","agent":"0xC750...9664","amount_raw":"1000000",
 "chain_id":42161,"contract":"0xdead...beef",
 "tx":{"data":"0xb6b55f25...f4240","from":"0xC750...","to":"0xdead...","value":"0x0"},
 "note":"Unsigned tx. Sign with your agent key ..."}

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— kcolbchain / Abhishek Krishna