On macOS trackpads, a light touch on a file/folder row can start a
native HTML5 drag after ~4px of movement, and Chromium then swallows
the resulting click. Track the drag start position and, on dragend,
treat a micro-drag (dropEffect 'none' and under 8px of travel) as the
click the gesture was meant to be.
Reconciled with main's OS file drag-drop upload handlers on the same
rows: kept onDrop/onDragOver/hasExternalFiles for external file
uploads, and wired the new click-recovery logic alongside it on both
the file tree row and the search-results row. Dropped the row's
cursor-grab/active:cursor-grabbing classes, since these rows are not
meant to read as draggable to the user.
Closes#2368
Bohdan Triapitsyn
69b39db427