Add AGENTS.md file to the repository

[lloc]

This PR introduces an AGENTS.md file to the repository. The file is designed to provide structured guidance for AI coding assistants and agents (such as GitHub Copilot, Cursor, or automated bots) working with the MultiSyde codebase.

Why Add AGENTS.md?

• Standardizes project knowledge in a way that is machine-readable.
• Helps AI assistants and automated tools understand the repository structure and conventions.
• Documents rules and constraints (e.g., do not modify build artifacts, plugin header, etc.).
• Provides a lean YAML summary at the bottom of the file for easier parsing by automated agents.
• Complements existing documentation (README.md, CONTRIBUTING.md, CHANGELOG.md) by being agent-focused.

Read on here → https://agents.md/

[InpsydeNiklas]

This looks great 👏
Minor suggestion: How about adding context for the runtime architecture in the summary for agents to better understand how features are discovered, loaded, and presented?

architecture:  
  bootstrap: src/Plugin.php  
  feature_loader: src/Modules.php  
  feature_config: modules/config.php  
  presenter: src/Presenter.php  
interfaces:  
  - LoadableFeature: required for all features  
  - ShareableInformation: optional for feature metadata  
data_structures:  
  - Summary: feature metadata container  
i18n:  
  text_domain: multisyde  
  template: languages/multisyde.pot  
admin:  
  menu_slug: multisyde  
  capability: manage_network