feat(agents): Minimal Coding Agent — Best Practices, Fundamentals, Security, Minimalism

### Chat Mode/Agent Name

MinimalCodingAgent

### Type

Custom Agent

### Purpose

Enable contributors to use a minimal coding agent (native Github custom agent) that enforces engineering excellence, security, and best practices, but only produces the smallest functional code avoiding overengineering and unnecessary documentation, editing/adding only the necessary files.

### Requirements

- Implement logic/code minimally and strictly to requirements
- Enforce repository conventional style and security rules
- Prohibit extra comments/documentation except for critical notes
- Discourage unnecessary abstractions, backwards compatibility, or non-essential features
- Is native GitHub custom agent

The issue names no files, tests, or existing agent entry point. Start by locating the repository's current custom-agent conventions and confirming the native GitHub custom-agent format. Done means a MinimalCodingAgent exists and its documented behavior covers minimal implementation, repository style and security rules, and avoidance of unnecessary additions.

Written by the indexing model from the issue text.