Add Nobulex: cryptographic accountability for AI agents (EU AI Act Ar…

[arian-gogani]

…t. 12)

Adds Nobulex to the Open-Source Tools section. Nobulex emits bilateral receipts (pre-execution + post-execution Ed25519 signatures) for EU AI Act Article 12 record-keeping compliance. Merged into Microsoft Agent Governance Toolkit (PRs #1302, #1333). 8 byte-match validated implementations across 7 organizations. AAIF Growth-stage proposal filed with TC sponsorship.

What are you adding or changing?

Checklist

• I have read CONTRIBUTING.md
• The link is publicly accessible and currently working
• The entry follows the format: - [Name](URL) — One-sentence description.
• The description is factual and under 100 characters (no marketing language)
• The resource is placed in the correct section
• The resource is not already listed in the README
• The resource is directly relevant to EU AI Act compliance or understanding