increased handle width in task panel (vibe-kanban) (#1202)

* Done! I've implemented the conditional width expansion solution for both resize handles.

**Changes made to [TasksLayout.tsx](file:///private/var/folders/5q/5vgq75y92dz0k7n62z93299r0000gn/T/vibe-kanban/worktrees/827f-handle/frontend/src/components/layout/TasksLayout.tsx):**

1. Added state tracking for panel sizes in both components
2. Updated `onLayout` handlers to track current panel sizes
3. Applied conditional styling: when panel < 5%, handle expands from 4px (`w-1`) to 24px (`w-6`)
4. Added smooth transitions between states

This fixes the grabability issue in both scenarios:
- Kanban/attempt handle (when kanban is collapsed)
- Attempt/aux handle in preview/diffs view (when attempt is collapsed)

* Perfect! I've updated the code to use the `onCollapse` and `onExpand` callbacks instead of size comparisons. The implementation is now cleaner and more semantic.

**Changes made:**
- Replaced size tracking with boolean collapsed state
- Added `onCollapse` and `onExpand` callbacks to both Panel components
- Updated handle styling to use `isKanbanCollapsed` and `isAttemptCollapsed` states
- Removed the size tracking logic from `onLayout` handlers

This approach is better because it directly uses the library's built-in collapse/expand events rather than inferring state from size values.

* Much better! I refactored the className to use the `cn` utility with multiple arguments for better readability. This is more idiomatic for Tailwind-based projects using shadcn/ui.

frontend/src/components/layout/TasksLayout.tsx

@@ -1,6 +1,7 @@
 import { ReactNode, useState } from 'react';
 import { PanelGroup, Panel, PanelResizeHandle } from 'react-resizable-panels';
 import { AnimatePresence, motion } from 'framer-motion';
+import { cn } from '@/lib/utils';
 
 export type LayoutMode = 'preview' | 'diffs' | null;
 
@@ -86,6 +87,7 @@ function RightWorkArea({
   const [innerSizes] = useState<SplitSizes>(() =>
     loadSizes(STORAGE_KEYS.ATTEMPT_AUX, DEFAULT_ATTEMPT_AUX)
   );
+  const [isAttemptCollapsed, setIsAttemptCollapsed] = useState(false);
 
   return (
     <div className="h-full min-h-0 flex flex-col">
@@ -114,6 +116,8 @@ function RightWorkArea({
               minSize={MIN_PANEL_SIZE}
               collapsible
               collapsedSize={0}
+              onCollapse={() => setIsAttemptCollapsed(true)}
+              onExpand={() => setIsAttemptCollapsed(false)}
               className="min-w-0 min-h-0 overflow-hidden"
               role="region"
               aria-label="Details"
@@ -123,7 +127,13 @@ function RightWorkArea({
 
             <PanelResizeHandle
               id="handle-aa"
-              className="relative z-30 w-1 bg-border cursor-col-resize group touch-none focus:outline-none focus-visible:ring-2 focus-visible:ring-ring/60 focus-visible:ring-offset-1 focus-visible:ring-offset-background"
+              className={cn(
+                'relative z-30 bg-border cursor-col-resize group touch-none',
+                'focus:outline-none focus-visible:ring-2 focus-visible:ring-ring/60',
+                'focus-visible:ring-offset-1 focus-visible:ring-offset-background',
+                'transition-all',
+                isAttemptCollapsed ? 'w-6' : 'w-1'
+              )}
               aria-label="Resize panels"
               role="separator"
               aria-orientation="vertical"
@@ -176,6 +186,7 @@ function DesktopSimple({
   const [outerSizes] = useState<SplitSizes>(() =>
     loadSizes(STORAGE_KEYS.KANBAN_ATTEMPT, DEFAULT_KANBAN_ATTEMPT)
   );
+  const [isKanbanCollapsed, setIsKanbanCollapsed] = useState(false);
 
   // When preview/diffs is open, hide Kanban entirely and render only RightWorkArea
   if (mode !== null) {
@@ -207,6 +218,8 @@ function DesktopSimple({
         minSize={MIN_PANEL_SIZE}
         collapsible
         collapsedSize={0}
+        onCollapse={() => setIsKanbanCollapsed(true)}
+        onExpand={() => setIsKanbanCollapsed(false)}
         className="min-w-0 min-h-0 overflow-hidden"
         role="region"
         aria-label="Kanban board"
@@ -216,7 +229,13 @@ function DesktopSimple({
 
       <PanelResizeHandle
         id="handle-kr"
-        className="relative z-30 w-1 bg-border cursor-col-resize group touch-none focus:outline-none focus-visible:ring-2 focus-visible:ring-ring/60 focus-visible:ring-offset-1 focus-visible:ring-offset-background"
+        className={cn(
+          'relative z-30 bg-border cursor-col-resize group touch-none',
+          'focus:outline-none focus-visible:ring-2 focus-visible:ring-ring/60',
+          'focus-visible:ring-offset-1 focus-visible:ring-offset-background',
+          'transition-all',
+          isKanbanCollapsed ? 'w-6' : 'w-1'
+        )}
         aria-label="Resize panels"
         role="separator"
         aria-orientation="vertical"