Add XR design guides for Sony, HTC, Pico, Samsung, and Valve platforms

[Copilot]

The repository lacked design guidelines from several major XR hardware manufacturers. This PR adds comprehensive design guides for five additional platforms based on their official documentation and industry research.

New Design Guides

Sony PlayStation VR2

• Eye tracking and foveated rendering
• Haptic feedback and Sense Controllers
• Play area safety and see-through view
• Ergonomic comfort and accessibility

HTC Vive

• World-space UI and spatial interactions
• Ergonomic positioning and fatigue reduction
• Multi-modal accessibility (gaze, gesture, voice)
• XRgonomics-based design principles

Pico VR

• OpenXR cross-platform compatibility
• Spatial-first design over 2D metaphors
• Hand tracking and controller support
• Performance optimization guidelines

Samsung Android XR

• Multimodal interaction (gaze, gesture, voice)
• Gemini AI integration
• Cross-device ecosystem interoperability
• Spatial canvas design principles

Valve SteamVR

• Chaperone boundary system
• FOV optimization and smooth transitions
• OpenXR compatibility
• Cross-hardware testing requirements

Each guide follows the existing repository format: TL;DR summary, 10 annotated bullet points, keywords section, and source citations. All files include proper Jekyll front matter for automatic website integration.

Structure

docs/
├── Sony/
│   ├── Sony.md
│   └── PlayStation VR2 Design Guidelines.md
├── HTC/
│   ├── HTC.md
│   └── HTC Vive XR Design Best Practices.md
├── Pico/
│   ├── Pico.md
│   └── Pico VR Design Guidelines.md
├── Samsung/
│   ├── Samsung.md
│   └── Samsung Android XR Design Principles.md
└── Valve/
    ├── Valve.md
    └── Valve SteamVR Design Best Practices.md

Original prompt

Look for design guides from major tech companies and summarize them into a condense and well structured guide

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