[Child] Update: Fix & Refresh README Files with Current Information

[ashleyshaw]

Parent Issue: #905

Overview

Implementation issue to fix and refresh in-scope README content and Mermaid diagrams after audit findings.

In-Scope

• Apply approved README content updates
• Fix Mermaid syntax and accessibility gaps
• Resolve broken links and stale references

Checklist

• Prioritised README remediation plan prepared
• Content/diagram fixes applied
• Spot validation completed

Deliverables

• Updated README files
• Remediation summary and verification notes

Related Files

• In-scope README files from audit inventory

[linear-code]

LS-987