fix: add fail-fast validation for partial Terms and Conditions genesis input (PM-22033)

[m2ux]

Overview

Addresses audit finding PM-22033 (Least Authority Node DIFF Audit, Feb 2026): partial Terms and Conditions genesis configuration is silently accepted instead of failing fast. When only one of the required values (hash or URL) is provided, genesis initialization skips without error, leaving storage uninitialized.

This PR adds explicit validation to reject partial input at genesis time and includes test coverage for the fail-fast behavior.

📐 Engineering

🗹 TODO before merging

• Implementation complete
• Tests pass
• Ready

📌 Submission Checklist

• Changes are backward-compatible (or flagged if breaking)
• Pull request description explains why the change is needed
• Self-reviewed the diff
• I have included a change file, or skipped for this reason:
• If the changes introduce a new feature, I have bumped the node minor version
• Update documentation (if relevant)
• Updated AGENTS.md if build commands, architecture, or workflows changed
• No new todos introduced

🧪 Testing Evidence

Please describe any additional testing aside from CI:

• Additional tests are provided (if possible)

🔱 Fork Strategy

• Node Runtime Update
• Node Client Update
• Other:
• N/A

Links

• Jira: PM-22033
• Parent Epic: PM-22039 — Q1 2026 Least Authority 'Node' (DIFF) Audit Findings
• Closes A2 Issue M: Partial Terms and Conditions Genesis Input Is Silently Accepted #1212