refactor(L1): remove legacy Nitro verifier

[leopoldjoy]

Summary

• remove the legacy NitroEnclaveVerifier, interface, tests, snapshots, and RISC Zero deployment script
• remove rollback-only deployment config/output wiring and the unused risc0-ethereum dependency
• preserve the hinted NitroValidator registration path, SP1 state-proof verification, and historical audit artifacts

Stack

• based on the squash-merged feat(L1): validate hinted Nitro attestations #399 commit
• the cleanup can proceed before rollout because none of the contract changes in this stack are deployed to a live system

Testing

• just deps
• just snapshots
• just semver-lock
• just test --match-path test/deploy/SystemDeploy.t.sol
• just test --match-path test/L1/proofs/TEEProverRegistry.t.sol
• just test --match-test test_cannotReinitialize_succeeds
• just test (1,206 passed, 0 failed, 1 skipped)

Linear: https://linear.app/coinbase/issue/CHAIN-4831/contracts-remove-the-legacy-nitro-zk-verifier-after-rollback-window

[linear]

CHAIN-4831

[cb-heimdall]

✅ Heimdall Review Status

Requirement	Status	More Info
Reviews	✅ 1/1	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 1 Additional review requirements Show calculation Max 0 0 From CODEOWNERS 0 Global minimum 0 Max 1 1 1 if commit is unverified 0 Sum 1