add(taxonomy): add Agentic Commerce terms

[galesky-a]

Summary

• Proposes 12 Agentic Commerce terms for initial taxonomy review.
• Only terms for now, definition and other fields tbd

Proposed terms

• Delegated payment
• Risk signal
• Agentic commerce
• Agentic commerce protocol
• Capability negotiation
• Mandate
• Agentic checkout
• Agent-mediated transaction
• Agent-initiated transaction
• Agent-completed transaction
• Human-present transaction
• Human-not-present transaction

Review status

This is a draft PR. These terms are proposed and are not yet accepted into the taxonomy. No definitions are proposed in this change.