Fix two-finger pan while drawing & Added panel resizing surface on mobile devices.

[AndrewSepic]

Fix Two-finger pan while drawing (Reported in #974)

• On touch devices (iPad, iPhone), two-finger pan/zoom gestures during line or polygon drawing were being swallowed by the drawing handlers, preventing Mapbox GL from navigating the map
• Root cause: touchstart unconditionally called e.preventDefault() and touchend unconditionally called handlers.click(), regardless of how many fingers were involved
• Fix adds an isMultiTouch ref in both useLineHandlers and usePolygonHandlers — when two or more fingers are detected, touch events are passed through to Mapbox GL rather than treated as drawing actions

How it works

• touchstart: if touches.length > 1, set isMultiTouch = true and return without calling preventDefault() — the map handles the gesture natively
• touchmove: bail out if multi-touch, so no phantom point updates during a pan
• touchend: skip click if isMultiTouch is set; reset the flag only once all fingers have lifted (handles the case where two fingers lift one at a time)

Closes #974

Fix Mobile Panel Resizability

• On a mobile device the horizontal panel at app bottom did not make a draggable surface visbille or available to click. Forcing the mobile user to not be able to resize the panel, and providing much reduced map surface.
• This adds CSS styles to ensure that the handle to resizing the panel is visible and can be used on Mobile devices.

Closes #986

Remove LegendContainer & Small Design artifact.

• There is a very small DOM element visible below the Legend, which was seen and after review this can be removed. I believe our refactor of the Placemark.io legend made this container un-neccesary.

Test plan

• On a touch device, enter line drawing mode, place a point, then use two fingers to pan/zoom — map should navigate without adding new points
• Confirm single-finger tap still adds points correctly
• Repeat for polygon drawing mode
• Confirm Apple Pencil drawing still works (existing force check in polygon handler is preserved)
• Confirm a that a draggable handle is visible and can be used on small devices to change the size of the bottom panel.

🤖 Generated with Claude Code

[chriswhong]

LGTM, actually tested this with an iPad and Apple pencil and an iPhone, everything works as expected.