Call from the input's pointerdown — non-primary buttons are ignored. Pass the WHOLE event: the
selection drag reads its target and position to place the caret itself (useTextSelectionDrag).
true while a pointer press OWNS the input — during the drag, and afterwards until the pointer
actually moves (HOVER_WAKE_DISTANCE). The second half is what makes a click dismiss:
the press leaves the pointer parked over the very text it just acted on, so without it the next
stray mousemove re-arms a hover tip in the same place — indistinguishable from the tip the user
clicked to get rid of. Moving the pointer at all is a deliberate hover and wakes it back up.
true while a pointer-driven text selection is in progress.
Wire to the input's dragstart: a press on the field means "select", never "move the text".
useSelectDrag's handle.