H010
An island has to load with the page for a reason its code could avoid: work that reaches past it, a module that runs as it loads, a box at module level, code the compiler can't see into. .kerf/hydration.json says why for every island.
Fix: /* @kerf visible */ above the component when its work only matters on screen, /* @kerf interaction */ when it only matters to someone using it; otherwise the fix the diagnostic names.
Status in kerf@0.1.0: reported by kerf check and by kerf routes --meta, per route, on what the routes produce.
More: kerf docs meta.