Add comprehensive AI assistant documentation and context

[Copilot]

Added documentation and inline comments to make the codebase accessible to AI coding assistants (GitHub Copilot, Cursor, Claude Code).

New Documentation

• ARCHITECTURE.md - System architecture, component relationships, data flow, threading model, and extension points
• .cursorrules - AI-specific project context: code style, naming conventions, hardware constraints, common patterns, and development guidelines
• CONTRIBUTING.md - Development setup, testing procedures, code standards, and common tasks
• README.md - Enhanced with feature highlights, hardware tables, MIDI/CV specifications, and technology stack

Enhanced Source Documentation

Added contextual comments to core files:

• main.cpp - Setup sequence, component initialization, screen switching logic
• board.h - Pin definitions organized by subsystem, output channel types, PWM/UART configuration
• urack_types.h - ScreenInterface pattern, lifecycle methods, usage examples
• signal_processor.h - MIDI→CV conversion, event types, calibration constants, threading model

Example: ScreenInterface Pattern

AI assistants can now understand the screen lifecycle pattern:

/**
 * ScreenInterface: Base class for all UI screens
 * 
 * Lifecycle:
 *   1. enter() - Called once when screen becomes active
 *   2. update() - Called repeatedly (processes input, redraws)
 *   3. exit() - Called once when leaving the screen
 */
class MyScreen : public ScreenInterface {
    void enter() override { /* Initialize */ }
    void update(Event* event) override { /* Handle input, redraw */ }
    void exit() override { /* Cleanup */ }
};

Total: ~1,200 lines of new documentation, ~470 lines of enhanced inline comments. Zero breaking changes.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• api.registry.nm1.platformio.org
  • Triggering command: /home/REDACTED/.local/bin/platformio platformio run (dns block)
• api.registry.platformio.org
  • Triggering command: /home/REDACTED/.local/bin/platformio platformio run (dns block)
• collector.platformio.org
  • Triggering command: /home/REDACTED/.local/bin/platformio platformio run (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

examine the project, it's purpose and architecture and make project vibecode friendly for tools like codex, Claude code, GitHub copilot and such

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💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.