DevNet 2.0: deploy develop's full contract set to OP Sepolia as a public-testnet dress rehearsal #284

Why

The live DevNet 1.0 (see sepolia_op_devnet in dincli/config/din_info.json) lists only the token, coordinator, stake and registry contracts, i.e. the pre-P3 generation. The treasury, fee router, emission and fair-launch distributor contracts, and all the P3/October fixes, have never been deployed to a real chain. The first real deployment will surface issues; better in a rehearsal than at public-testnet launch.

Scope

1. Deploy develop's contracts to OP Sepolia with DeployPlatform.s.sol, using the agreed Decide and set testnet tokenomics parameters: mintCap, dinPerEth, and DinEmission values #155 values.
2. Run full GIs end to end with the MNIST model: clients, auditors, aggregators, emission funding, validator reward claims, and a dispute.
3. Update dincli/config/din_info.json and the participant docs with the new addresses.
4. Record real gas costs per role (feeds Simulation: model validator gas costs to size ETH network fee for model trainers #78).
5. Decide key custody: who holds the deployer and ProxyAdmin keys for the public testnet (e.g. hardware wallet or Safe), and record it in the incident runbook (Incident response runbook and incident communication for testnet #167).
6. Verify the deployment matches the repo (deployment drift check, BL-33 / PR feat(tooling): dincli system verify-deployment — on-chain drift check (issue #244) #254).

Depends on

#223 (model-owner deploy), the setup-guide install fix, the data-owner reward default (client share 0% at launch), and ideally #238 and #222.

Done when

A full GI completes on OP Sepolia with develop's contracts, and a newcomer can join by following the docs alone.