perf(virtual-list): improve height estimates with variant-specific calculations

- Replace generic 50px estimate with variant-specific heights
- Add browser-tested calculations: Calendar(32px), Compact(68px), Subtask(48px), Kanban(110px), Default(120px)
- Account for MaterialCard padding + content height + TaskItem mb-2 margin
- Update test environment to use same variant-specific estimates
- Maintain dynamic measureElement for fine-tuning

Improves initial virtual list rendering accuracy and scroll performance.

Author: dohsimpson

apps/web/components/task/virtualized-task-list.tsx

@@ -85,10 +85,34 @@ export function VirtualizedTaskList({
   // Get tasks in sorted order for virtualization
   const sortedTasks = sortedTaskIds.map((id) => tasks.find((t) => t.id === id)).filter(Boolean)
 
+  // Variant-specific height estimates based on actual browser calculations
+  // Formula: MaterialCard padding + content height + TaskItem mb-2 margin (8px)
+  const getEstimateSize = useCallback(() => {
+    switch (variant) {
+      case "calendar":
+        // p-1 (8px total) + minimal content (~16px) + mb-2 (8px) ≈ 32px
+        return 32
+      case "compact":
+        // p-2.5 (20px total) + single row content (40px) + mb-2 (8px) = 68px
+        return 68
+      case "subtask":
+        // p-2 (16px total) + subtask content (~24px) + mb-2 (8px) ≈ 48px
+        return 48
+      case "kanban":
+        // Empirically tested: 110px works better
+        return 110
+      case "default":
+        // p-4 (32px total) + full content (80px) + mb-2 (8px) = 120px
+        return 120
+      default:
+        return 68 // Sensible fallback
+    }
+  }, [variant])
+
   const virtualizer = useVirtualizer({
     count: sortedTasks.length,
     getScrollElement,
-    estimateSize: () => 50,
+    estimateSize: getEstimateSize,
     overscan: 5,
   })
 
@@ -130,7 +154,7 @@ export function VirtualizedTaskList({
 
   // In test environment, render all items to make them available for queries
   const itemsToRender = isTest
-    ? sortedTasks.map((task, index) => ({ task, index, start: index * 50 }))
+    ? sortedTasks.map((task, index) => ({ task, index, start: index * getEstimateSize() }))
     : virtualizer
         .getVirtualItems()
         .map((vi) => ({ task: sortedTasks[vi.index], index: vi.index, start: vi.start }))