💎 "Obsidian" UI & Architecture Overhaul

• Nexus Core Engine (SSOT Architecture): Core workspace management is now entirely handled by pure Rust + NAPI-RS. React is demoted to a stateless rendering layer, completely eliminating state tearing across components.
• High-Speed PTY Binary Pipeline: A multithreaded Rust layer now directly captures PTY streams, completely bypassing JSON serialization. Raw binary buffers pierce straight into V8, maintaining a locked 60fps even when bursting tens of thousands of log lines per second.
• Seamless Multi-Window Tear-off: Refactored pane detachment logic. Terminals and plugins can now be "torn off" like sticky notes onto external monitors. The underlying nexusReplacePane handshake ensures zero runtime context loss.
• Full-Space Glassmorphism Aesthetics: Abandoned rigid borders for deeply customized acrylic blur materials (backdrop-filter) and transparent scrollbars, seamlessly intertwining system lights with code.
• Twin-Star Offline Typography: Removed external Google Fonts network dependencies to eliminate layout shifts. Alphanumerics use the futuristic, open-source Reddit Sans, while Chinese characters are beautifully rendered using Xiaomi's ultra-smooth MiSans. The WebGL terminal strictly retains its Fira Code monospace isolation.
• getssh-plugin:// Protocol Sandbox: Third-party plugins are now strictly loaded via a custom protocol, thoroughly blocking unauthorized local system API abuse.
• Ultimate Cross-Origin XSS Defense: Forced intervention in window.parent.postMessage tunnels. The Electron Main process now performs strict PARENT_ORIGIN validation, instantly intercepting privilege escalation attempts.
• Ghost Tabs & Dead Connection Awareness: Fixed resurrected tabs and bouncing sizes via high-speed reverse IPC feedback (nexusCloseTab, nexusUpdateSizes). Precise "disconnected" masks are now rendered instantly upon server disconnects to prevent misoperations.