feat(zeronet): add Nitro validator cutover task

[leopoldjoy]

Summary

• add the active Zeronet task that deploys P384Verifier, CertManager, NitroValidator, and TEEProverRegistry v0.6.1
• configure the incident multisig as CertManager owner and the existing Keychain-backed registrar signer as revoker
• add signer-facing forward and pre-signed rollback flows through the nested ProxyAdmin Safe hierarchy
• preserve and validate registry ownership, management, proposer, signer, game type, and image-hash state across the implementation change
• document registrar/enclave cutover and immediate rollback procedures

Deployment workflow

This PR follows the current task-branch workflow. It should remain open while the facilitator deploys the contracts, generates the four validation files, collects signatures, executes the task, commits records, and archives the completed task before merge.

Verification

• installed task dependencies from BASE_CONTRACTS_COMMIT=8897196c2a77b04fe69e47e158c6c112a936d65c
• compiled the Nitro stack with the 10,000-run Cancun deployment profile
• compiled the registry with the 999,999-run metadata-free Cancun profile
• verified the registry init-code hash matches the contracts semver lock: 0x380af47d78626bd0af4bb45769a9c184d6ea22adf60877ea9765129a28a3ffd6
• deployed all four contracts successfully on an Anvil fork of live Zeronet
• simulated forward and future-nonce rollback signer payloads against the fork
• verified the existing shared common-script CI build remains compatible with its current contracts pin

Pending facilitator artifacts

Per repository policy, addresses.json, generated validation JSONs, and execution records will be added after the real Ledger deployments and signer-tool generation.

[cb-heimdall]

✅ Heimdall Review Status

Requirement	Status	More Info
Reviews	✅ 2/2	Denominator calculation Show calculation 1 if user is bot 0 1 if user is external 0 2 if repo is sensitive 0 From .codeflow.yml 2 Additional review requirements Show calculation Max 0 0 From CODEOWNERS 0 Global minimum 0 Max 2 2 1 if commit is unverified 0 Sum 2

Approved review 4975262261 from roger-bai-coinbase is now dismissed due to new commit. Re-request for approval.