feat: add AGENTS.md documentation for each scope level

[p-iknow]

Context

Currently there is no AGENTS.md documentation in the project. The meta-agent-creator skill exists at .claude/skills/meta-agent-creator/ but lacks comprehensive documentation on agent scopes and their usage patterns.

According to official Claude Code documentation, agents have 4 scope levels with different priorities:

• CLI-defined (--agents flag): Current session only, Priority 1
• Project (.claude/agents/): Current project, Priority 2
• User (~/.claude/agents/): All projects, Priority 3
• Plugin (<plugin>/agents/): Where plugin is enabled, Priority 4

Requirement

Create AGENTS.md documentation for each scope level to guide users on:

• When to use each scope
• How to configure agents at each level
• Best practices for scope selection
• Priority and override behavior

Solution

Test Plan

Reference

• .claude/skills/meta-agent-creator/SKILL.md
• https://code.claude.com/docs/en/sub-agents