docs: add ERC-8183 job lifecycle example for Arc Testnet

[consumeobeydie]

Summary

This PR adds a practical ERC-8183 agentic commerce job lifecycle example to the Arc Testnet documentation.

What's included

• Complete ERC-8183 job lifecycle: createJob → setBudget → approve → fund → submit → complete
• Circle Developer-Controlled Wallets integration
• Live on-chain proof with all transaction hashes

Live Example

Tested and verified on Arc Testnet:

• Job ID: 110860
• Status: Completed
• Budget: 5 USDC

Related PRs

This PR completes the agentic stack trilogy:

• docs/foundry-smart-contract-deploy-guide (Solidity contracts)
• docs/x402-arc-agent-example (X402 payments)
• docs/erc8004-agent-registration-example (ERC-8004 identity)
• docs/erc8183-job-lifecycle-example (ERC-8183 jobs) ← this PR

Full repository: https://github.com/consumeobeydie/arc-agent-api

[osr21]

Real-world ERC-8183 implementation report — Arc Stablecoin DApp

We built a full ERC-8183 Agentic Commerce implementation on Arc Testnet as part of the Arc Stablecoin DApp (live demo). Sharing our findings to complement this PR.

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Deployed contract

AgenticCommerce at 0x0Ecdad8fdA2Dde60E475e70Ebf177F2299FECB48 — Arc Testnet (Chain 5042002).

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Gas limits — Arc requires higher than standard EVM

The most important gotcha. Arc's opcode costs are higher than standard EVM. Default estimateGas values will revert silently:

Operation	Required gas
createJob()	400,000 minimum
bid(), acceptBid(), submitDeliverable(), approveDeliverable(), cancelJob()	200,000 minimum

We hardcode these limits rather than relying on estimateGas for Arc. The on-chain cost of approveDeliverable (one SSTORE + one ERC-20 transfer) was 69,707 gas in practice, but estimation was unreliable.

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Custom error selectors to decode in the frontend

Selector	Error	When it fires
0x82b42900	Unauthorized()	Wrong role — client tried to bid on own job, or non-provider tried to submit deliverable
0x70f65caa	DeadlinePassed()	Job deadline expired — bidding / submission closed
0x0d2f0676	AlreadyBid()	This address already has an active bid on the job
0xff97b861	ZeroBudget()	Budget must be > 0 when creating a job

Decode pattern: take bytes [2..10] from the raw revert hex string (first 4 bytes after 0x).

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Double Transfer event on Arc — don't double-count

When approveDeliverable() releases USDC from escrow, two Transfer events fire in the same tx:

1. Arc native precompile mirror at 0xfffffffffffffffffffffffffffffffffffffffe
2. USDC ERC-20 address 0x3600000000000000000000000000000000000000

Both represent the same single transfer. Filter by the ERC-20 address (0x3600...) when parsing receipts to avoid counting it twice.

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On-chain proof — complete lifecycle

Successful approveDeliverable(jobId=3): 0x68fbe19d586bf43c29f003a85610650ea06270fb2b71ca04263bb150e8ce22e9

• Gas used: 69,707 / 200,000
• 3 logs: native precompile Transfer + ERC-20 Transfer + DeliverableApproved

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UI role-enforcement patterns

Pre-emptive UI guards prevent most reverts before they reach the chain:

• Hide bid() button when connectedWallet === job.client
• Disable submitDeliverable unless connectedWallet === job.provider
• Disable bid() when block.timestamp >= job.deadline
• Disable approveDeliverable / cancelJob unless connectedWallet === job.client