Restore the Clash chatbot avatar across brand surfaces

[hrhrng]

What changed

• restores the Clash chatbot avatar across desktop, favicon, product navigation, login, animated/error marks, install icons, Open Graph image, and GitHub social preview
• removes the incorrect standalone C brand variants and their cache-busted consumers
• adds a regression contract that locks the desktop and browser surfaces to the chatbot avatar

Why

The previous brand pass replaced the product avatar with a generic coral C. The actual Clash identity is the chatbot face with two eyes and the coral slash.

Validation

• RED: the new logo contract failed against the C assets
• GREEN: 30 focused desktop/Web brand tests pass
• macOS universal DMG built successfully with Node 22.22.0 and pnpm 10.34.5
• packaged ICNS SHA-256 matches the restored source ICNS
• packaged executable contains x86_64 arm64
• hdiutil verify reports the rebuilt DMG as valid