Summary

Remove Checkov and Mermaid CLI from the documented tool list in the devcontainer README since neither tool is installed in the current devcontainer configuration or copilot-setup-steps workflow.

Acceptance Criteria

• Checkov removed from .devcontainer/README.md tool matrix or equivalent documentation
• Mermaid CLI removed from .devcontainer/README.md tool matrix or equivalent documentation
• No documentation references to these tools remain unless they describe a deliberate removal decision
• If documentation listed other tools that are not installed, those are also removed or flagged

Context

The devcontainer documentation lists Checkov and Mermaid CLI as available tools, but neither appears in on-create.sh, post-create.sh, devcontainer.json features, or copilot-setup-steps.yml. This creates confusion about the actual development environment capabilities.