Position the spawn modal directly under the 'New Agent' button without a
blur overlay. Uses click-outside dismissal and absolute positioning.
Reduces visual disruption for quick agent spawning.
Closes bd-4lc. When navigating with arrow keys, the selected item now
scrolls into view using scrollIntoView({ block: 'nearest' }) to prevent
jarring scrolls when item is already visible.
Closes bd-3ny. Added mousedown listener that dismisses the dropdown when
clicking outside both the dropdown and textarea. Uses early return to avoid
registering listeners when dropdown is already closed.
