Post-demo hardening: reject init calldata when init address is zero

[claude-do]

Track diamond init-call hardening.

Expected follow-up:

• If init == address(0), require data.length == 0.
• Add a focused diamondCut test for data-with-zero-init rejection.

Full triage doc: https://github.com/OmniPass-world/clan-world/blob/fix/diamond-init-finalize-guard/docs/reviews/pr468-gpt-5-5-pro-followup.md

Immediate fix PR: #475