Help tooltips were CSS pseudo-elements on the info icon, so they were
descendants of the scrollable settings pane (.settings-content uses
overflow-y: auto) and got clipped at its top edge. The Active Library
deprecation notice made this obvious: the text grew to ~10 lines while
only ~5 fit above the icon, so the tooltip started mid-sentence at
"page. Deprecated:".
Render the tooltip once into <body> with position: fixed instead, so no
overflow ancestor can clip it, and position it from JS: above the trigger
when it fits, below otherwise, clamped to the viewport. It follows the
trigger on scroll/resize and hides on mouseout, Escape or touch. The
delegated listeners also cover help icons rendered later by the settings
manager, and the box may now use 320px instead of 220px, which keeps long
help texts to fewer lines.
