fix(ui): sidebar resize handle touch area + linked doc border styling

ResizeHandle: the v0.14.5 archive browser PR simplified the touch area
to treat both sides identically, making the left sidebar handle
ungrabable. Now uses asymmetric positioning per side — extends slightly
toward the panel, more toward the content, without covering scrollbars.

Viewer: linked doc border reduced from 2px full-opacity primary to 1px
at 40% opacity for a subtler visual distinction.

For provenance purposes, this commit was AI assisted.

Author: backnotprop

packages/ui/components/ResizeHandle.tsx

@@ -3,9 +3,9 @@ import type { ResizeHandleProps as BaseProps } from '../hooks/useResizablePanel'
 
 interface Props extends BaseProps {
   className?: string;
-  /** When set, touch area extends rightward only to avoid covering adjacent scrollbars.
-   *  Both 'left' and 'right' produce the same behavior — scrollbars sit on the right
-   *  edge of left-adjacent panels, so the handle must never extend leftward. */
+  /** Controls which direction the touch area extends to avoid covering adjacent scrollbars.
+   *  'left' = handle is on the right edge of the left sidebar, touch area extends leftward.
+   *  'right' = handle is on the left edge of the right panel, touch area extends rightward. */
   side?: 'left' | 'right';
 }
 
@@ -24,10 +24,12 @@ export const ResizeHandle: React.FC<Props> = ({
     <div className={`absolute inset-y-0 -left-0.5 -right-0.5 transition-colors ${
       isDragging ? 'bg-primary/50' : 'group-hover:bg-border'
     }`} />
-    {/* Wider touch area — extends rightward to avoid covering left-side scrollbars */}
+    {/* Wider touch area — extends away from adjacent scrollbar */}
     <div
       className={`absolute inset-y-0 ${
-        side ? 'left-0 -right-3' : '-inset-x-2'
+        side === 'left' ? '-right-2 -left-1' :
+        side === 'right' ? '-left-2 -right-1' :
+        '-inset-x-2'
       }`}
       onMouseDown={onMouseDown}
       onTouchStart={onTouchStart}

packages/ui/components/Viewer.tsx

@@ -429,7 +429,7 @@ export const Viewer = forwardRef<ViewerHandle, ViewerProps>(({
       <article
         ref={containerRef}
         className={`w-full bg-card rounded-xl shadow-xl p-5 md:p-8 lg:p-10 xl:p-12 relative ${
-          linkedDocInfo ? 'border-2 border-primary' : 'border border-border/50'
+          linkedDocInfo ? 'border border-primary/40' : 'border border-border/50'
         } ${inputMethod === 'pinpoint' ? 'cursor-crosshair' : ''}`}
         style={{ WebkitTouchCallout: 'none' } as React.CSSProperties}
       >