Combines the 'edit' fix with feat/mel-osp-changes (6fd6ad4), which
refactored ExecutionContext to {targetParentChainBlockHash,
initialWasmModuleRoot}. Passes both as HashZero for the proof fixtures
and drops the now-unused inboxLimit/bridge.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

OneStepProverHostIo now takes (customDAValidator, hashProofHelper); the deploy
script only passed one arg, failing hardhat-deploy with "expected 2 constructor
arguments, got 1" and breaking the OneStepProof proof-validation tests.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Non-MEL halted proofs serialize only the global state (the prover reads no
further), so unconditionally deserializing a MELState ran past the proof end
and reverted with Panic(0x32) for every terminal step. Gate the MELState read
and kickstart logic on a non-zero MELStateHash.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>