Floating Island Navbar

One file, zero dependencies, a client component. The islands are glass capsules: a translucent fill, a backdrop filter, an inner top highlight and a soft shadow. The two header states are told apart by the data-scrolled attribute on the dock: at the top the islands stand on their own and the bar is wider, once scrolled the island fills fade while the shared bar takes the glass, the shadow and a narrower width. The active-item glider is a separate layer under the links, positioned from offsetLeft/offsetWidth and following cursor and focus; until the JS is ready the active item keeps a plain background, so the highlight never disappears before hydration. The action button carries a glow that tracks the cursor. The mobile menu closes on Escape and on an outside click. The layout is a container query on the block's own width. All motion is removed under prefers-reduced-motion. Palette --vibeui-navbar-010-*.