docs: add ADR 0023 for Evidence Mapping structure [WIP]

[jpower432]

Description

Introduced a new ADR for Evidence Mapping, detailing the structure and purpose of the #EvidenceMapping type. This replaces the previous #Evidence definition to better capture evidence source references and their integrity.

Schema Changes

Schema Changes Made

• No schema changes
• Audit Log schema (auditlog.cue) changes
• Capability Catalog schema (capabilitycatalog.cue) changes
• Control Catalog schema (controlcatalog.cue) changes
• Enforcement Log schema (enforcementlog.cue) changes
• Evaluation Log schema (evaluationlog.cue) changes
• Guidance Catalog schema (guidancecatalog.cue) changes
• Mapping Document schema (mappingdocument.cue) changes
• Policy Document schema (policy.cue) changes
• Principle Catalog schema (principlecatalog.cue) changes
• Risk Catalog schema (riskcatalog.cue) changes
• Threat Catalog schema (threatcatalog.cue) changes
• Vector Catalog schema (vectorcatalog.cue) changes
• Other

Schema Change Details

<!-- If applicable, provide a brief summary or example of schema changes -->

Testing

• Unit tests added/updated
• Manual testing performed
• Test data updated (if applicable)

Related Issues

Ref: #421

Reviewer Hints

---

Self-review checklist

• This PR has content that was created with AI assistance.
  • I have read and followed the Generative AI Contribution Policy.
• I have the experience and knowledge necessary to answer maintainer questions about the content of this PR, without using AI.