[Improvement]: Expand glossary to cover missing repository terminology

[aurelienlair]

File or section being improved

docs/glossary.md

The gap

While reviewing the repository documentation, I identified a discrepancy between the terminology used in the README and playbooks and the definitions available in docs/glossary.md. Currently, several technical terms and roles are utilized throughout the repo without a centralized definition, which may lead to ambiguity for both human contributors and automated agents attempting to resolve these concepts.

Proposed change

Update docs/glossary.md to include clear, concise definitions for the following terms:

• x402 facilitator: Define the role and technical context as referenced in /examples/README.md and /protocols/x402.md.
• Quote-vs-settle drift: Provide a technical explanation of this variance to ensure a shared understanding of the concept.
• Buyer agent vs. Seller agent: Explicitly define these roles as they are used in the /agent-playbooks.

Mock mode: Define the purpose and behaviour of the MOCK_MODE=true flag used in /examples to assist users in testing and exploration.

Public reference

• docs/glossary.md
• /examples/README.md
• /protocols/x402.md
• /agent-playbooks/

Public reference

No response

Submission checklist

• One change per PR — this proposal is a single scoped edit
• No marketing language in the proposed text
• Official source linked for any factual claim
• I have read CONTRIBUTING.md