Add CODEOWNERS file for automatic reviewer assignment

[EricGrill]

Problem

No CODEOWNERS file exists for automatic reviewer assignment.

Current state:

• No .github/CODEOWNERS file
• No automatic reviewer assignment for PRs
• Review burden likely falls entirely on @EricGrill

Why it matters:
As the project grows, manual reviewer assignment doesn't scale. CODEOWNERS ensures:

• Domain experts review relevant changes
• Faster review turnaround
• Clear ownership of different areas
• Reduced burden on single maintainer

Suggested Solution

Create .github/CODEOWNERS with patterns like:

# Global fallback
* @EricGrill

# Plugin categories
/plugins/anthropic-* @EricGrill
/plugins/mcp-* @EricGrill
/plugins/superpowers/ @EricGrill

# Core infrastructure
/.github/ @EricGrill
/schemas/ @EricGrill
/scripts/ @EricGrill

# Documentation
/README.md @EricGrill
/CONTRIBUTING.md @EricGrill
/PROJECT-STATUS.md @EricGrill

Acceptance Criteria

• .github/CODEOWNERS file created
• Key areas have designated owners
• Global fallback owner specified
• File referenced in CONTRIBUTING.md

[EricGrill]

Triage: Roadmap ✅

Decision: Add to Q2 roadmap.
Milestone: v1.0.0 — Repo Foundation
Priority: P2
CODEOWNERS is low-effort governance improvement that scales reviewer assignment as the project grows.