Add macOS support with native Cocoa overlay window

[m31-galaxy]

Summary

This PR adds full macOS support to Hexecute by implementing a native Cocoa backend alongside the existing Wayland/Linux implementation. The app now runs on both Linux and macOS with platform-specific windowing and input handling.

Key Changes

• New Cocoa Backend (pkg/cocoa/): Implements a transparent, borderless fullscreen overlay window using native macOS APIs

  • cocoa.m: Core Cocoa implementation with OpenGL 4.1 context, event handling, and input management
  • cocoa.h: C header defining the public Cocoa API
  • cocoa.go: Go wrapper providing the platform-agnostic CocoaWindow type

• Platform Abstraction Layer (internal/platform/): Introduces a Window interface to decouple platform-specific code from the rest of the application

  • window.go: Defines the common Window interface
  • window_linux.go: Linux implementation using Wayland backend
  • window_darwin.go: macOS implementation using Cocoa backend

• Updated Core Modules: Refactored to use the platform-agnostic Window interface instead of directly depending on wayland.WaylandWindow

  • internal/draw/draw.go
  • internal/update/update.go
  • internal/execute/execute.go
  • cmd/hexecute/main.go

• Build System Updates (flake.nix): Extended Nix flake to support multiple platforms

  • Added support for x86_64-linux, aarch64-linux, x86_64-darwin, and aarch64-darwin
  • Conditional dependencies: Wayland/X11 libs only on Linux; Cocoa/OpenGL frameworks provided by macOS stdenv
  • macOS-specific postInstall step to create a proper .app bundle with metadata

• macOS App Bundle: Added proper application metadata and icon

  • macos/Info.plist: Bundle configuration (version, identifier, minimum OS, etc.)
  • macos/Hexecute.icon/: Icon asset definition and PNG source

• CI/CD Updates (.github/workflows/build.yml): Extended to build on both Ubuntu and macOS

  • Separate artifact uploads for each platform
  • macOS builds produce a .tar.gz of the .app bundle (preserving executable bits)

• Documentation Updates (README.md): Added macOS build and usage instructions

Implementation Details

• Coordinate System Consistency: The Cocoa backend uses logical points (not backing pixels) to match the Wayland backend's coordinate space, ensuring gl_FragCoord, resolution uniforms, and cursor coordinates all align
• Key Mapping: macOS virtual key codes are translated to XKB keysyms for cross-platform consistency
• Input Handling: Supports mouse movement, button clicks, and keyboard input (currently Escape key) with an input disable mechanism for exit animations
• Window Properties: Borderless, fullscreen, transparent overlay with status window level; hides system cursor while active
• Build-Tagged Files: Platform-specific code is cleanly separated using Go build tags (//go:build darwin and //go:build linux)

https://claude.ai/code/session_01LjKPHZaHPxMhLXGe55hMeW