Add project architecture planner

[goldirana]

Pull Request Checklist

• I have read and followed the CONTRIBUTING.md guidelines.
• I have read and followed the Guidance for submissions involving paid services.
• My contribution adds a new instruction, prompt, agent, skill, or workflow 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, agent, skill, or workflow with GitHub Copilot.
• I have run npm start and verified that README.md is up to date.
• I am targeting the staged branch for this pull request.

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Description

Adds a Project Architecture Planner agent that fills a gap in the existing architecture-related agents. Currently, users need to consult 3-5 different agents (arch.agent.md, se-system-architecture-reviewer.agent.md, azure-principal-architect.agent.md, etc.) to get holistic architecture guidance. This agent consolidates that into a single, structured workflow.

What it does:

• Discovery-first approach — gathers business context, scale expectations, team composition, and budget before making any recommendations
• Tech stack evaluation — scores options against team fit, ecosystem maturity, scalability, cost, and hiring market (cloud/language agnostic)
• Scalability roadmap — phased plan from MVP → Growth → Scale with architecture diagrams at each stage
• Cost analysis — cloud-agnostic cost modeling, optimization strategies, and multi-cloud comparison
• Existing codebase review — audits for architectural debt, bottlenecks, and modernization paths
• Three diagram output formats: Mermaid in Markdown, interactive HTML preview page (with dark/light mode), and Draw.io .drawio XML export

Why it's needed: No existing agent combines tech stack evaluation, scalability planning, cost modeling, and best practices synthesis into one cohesive plan. The closest agents are domain-specific (Azure-only, cloud-only, code-level only).

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Type of Contribution

• New instruction file.
• New prompt file.
• New agent file.
• New plugin.
• New skill file.
• New agentic workflow.
• Update to existing instruction, prompt, agent, plugin, skill, or workflow.
• Other (please specify):

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Additional Notes

• The agent references other existing agents (arch.agent.md, se-system-architecture-reviewer.agent.md, azure-principal-architect.agent.md) for deep dives, promoting discoverability of the collection.
• Diagrams use securityLevel: 'strict' in the HTML output to prevent XSS.
• No paid services or external dependencies required.

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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.

[github-actions]

🔍 Skill Validator Results

2 resource(s) checked | ✅ All checks passed

Full output

No agents found in the specified paths: "/home/runner/work/awesome-copilot/awesome-copilot/agents/project-architecture-planner.agent.md"

Note: Errors were found. These are currently reported as warnings and do not block merge. Please review and address when possible.