chore: myco v1 global upgrade

Removed embedded Myco agent scripts and their configurations across multiple agents.
This streamlines tooling by relying on a global Myco installation instead of project-level managed wrappers.

Key changes include:
*   Removed agent runner scripts and skill symlinks.
*   Eliminated the dedicated plugin for OpenCode.
*   Updated agent configurations to remove Myco-specific hooks and permissions.
*   Simplified Myco's local `.gitignore` configuration.

Author: sirkirby