📋 docs: Create agent quick-reference cheatsheet

[njueeRay]

Description

OpenProfile uses a team of AI Agents (Brain, PM, Dev, Code-Reviewer, Researcher, Profile-Designer, Brand) to collaboratively build a GitHub Profile. The agent definition files in .github/agents/ are a core differentiator.

However, new users have no easy way to understand what agent to use for what task. A quick-reference cheat sheet would lower the barrier to entry.

What to do

Create docs/agent-cheatsheet.md with:

1. One-line summary of each agent's role
2. When to use each agent (use-case based, not role-based)
3. Example prompts for common tasks:
   • "I want to add a new section to my profile" → which agent?
   • "I want to check if my PRs badge is broken" → which agent?
   • "I want to plan my next sprint" → which agent?
4. Agent interaction diagram (simplified Mermaid or ASCII)

Reference

• Agent files: .github/agents/*.agent.md
• Agent workflow doc: docs/agent-workflow.md
• Team playbook: docs/team-playbook.md

Acceptance criteria

• docs/agent-cheatsheet.md created
• All 7 agents covered
• At least 5 example prompts with recommended agent
• Written in English (primary) with optional Chinese notes