chore(chatmodes): HLBPA chat mode updates

[anchildress1]

• Standardized YAML front-matter formatting and tool list quoting in hlbpa.chatmode.md
• Clarified and enforced Mermaid-only diagram requirement in HLBPA chat mode

Assisted-by: GitHub Copilot

Pull Request Checklist

• I have read and followed the CONTRIBUTING.md guidelines.
• My contribution adds a new instruction, prompt, or chat mode file in the correct directory.
• The file follows the required naming convention.
• The content is clearly structured and follows the example format.
• I have tested my instructions, prompt, or chat mode with GitHub Copilot.
• I have run node update-readme.js and verified that README.md is up to date.

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Description

Minor edits to original to correct complaining GFM format to frontmatter and clarify questions regarding diagram output choices.

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Type of Contribution

• New instruction file.
• New prompt file.
• New chat mode file.
• Other (please specify): Edits to fix existing HLBPA chat mode

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Additional Notes

Mostly fixing the GH render complaints, but also clarified diagram direction.

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By submitting this pull request, I confirm that my contribution abides by the Code of Conduct and will be licensed under the MIT License.