Disable drag-out-of-toolbar for pen inputs

Problem

When using a pen/stylus to select tools in the toolbar, the drag-out-of-toolbar feature often triggers false positives. Small movements while tapping with a pen are interpreted as drag gestures, causing shapes to be created unintentionally. This creates a distracting experience when trying to simply select tools with a stylus.

Proposed solution

Disable the drag-out-of-toolbar functionality entirely for pen-type inputs (e.pointerType === 'pen'). The relevant code is in useDraggableEvents in TldrawUiMenuItem.tsx - it should check for pen input early and skip the drag handling path.

Why this makes sense

• Pen users typically want precise control and are clicking to select tools, not drag
• The existing drag threshold doesn't account for the slight movements inherent in pen input
• Mouse and touch users can still benefit from drag-out-of-toolbar
• This is a simple, targeted fix with no impact on other input types