Handle context menu events in header cells

packages/frontend-core/src/components/sheet/cells/HeaderCell.svelte

@@ -18,15 +18,24 @@
   $: canMoveLeft = orderable && column.idx > 0
   $: canMoveRight = orderable && column.idx < $columns.length - 1
 
-  const startReordering = e => {
+  const onMouseDown = e => {
+    if (e.button === 0 && orderable) {
       timeout = setTimeout(() => {
         reorder.actions.startReordering(column.name, e)
       }, 200)
     }
+  }
 
-  const stopReordering = () => {
+  const onMouseUp = e => {
+    if (e.button === 0 && orderable) {
       clearTimeout(timeout)
     }
+  }
+
+  const onContextMenu = e => {
+    e.preventDefault()
+    open = true
+  }
 
   const sortAscending = () => {
     sort.set({
@@ -66,8 +75,9 @@
   <SheetCell
     reorderSource={$reorder.sourceColumn === column.name}
     reorderTarget={$reorder.targetColumn === column.name}
-    on:mousedown={orderable ? startReordering : null}
+    on:mousedown={onMouseDown}
-    on:mouseup={orderable ? stopReordering : null}
+    on:mouseup={onMouseUp}
+    on:contextmenu={onContextMenu}
     width={column.width}
     left={column.left}
   >

packages/frontend-core/src/components/sheet/cells/SheetCell.svelte

@@ -39,6 +39,7 @@
   on:mousedown
   on:mouseup
   on:click
+  on:contextmenu
   {style}
   data-row={rowIdx}
 >