Bundle Lucide (ISC license) at assets/fonts/lucide.ttf and register it as the
egui font family "lucide" via mobile/icons.rs::install (called in EditorApp::new).
Icons are drawn as text with icons::font(size) + PUA codepoint constants.
Switch the stack headers (grip, maximize/minimize, node⇄instrument), the footer
chevron, and the transport play/pause to Lucide glyphs instead of relying on
egui's limited built-in emoji-icon-font.
Skyler Lehmkuhl