fix(grid): scope header generate-value to the clicked column

apps/desktop/src/components/grid/DataGrid.vue

@@ -5784,6 +5784,7 @@ const {
   restoreCellSelectionState,
   cellIsSelected,
   columnIsSelected,
+  columnIsExclusivelySelected,
   selectedRangeStart,
   selectedRowIds,
   selectedColumnIndexes,
@@ -10543,7 +10544,7 @@ watch(
 function onHeaderContext(col: string, columnIndex: number) {
   invalidateContextMenuTarget();
   const visibleColIdx = visibleColumnIndexes.value.indexOf(columnIndex);
-  if (visibleColIdx >= 0 && !columnIsSelected(visibleColIdx)) {
+  if (visibleColIdx >= 0 && !columnIsExclusivelySelected(visibleColIdx)) {
     selectColumn(visibleColIdx);
   }
   contextHeaderColumn.value = col;

apps/desktop/src/composables/__tests__/useDataGridSelection.spec.ts

@@ -122,6 +122,38 @@ describe("useDataGridSelection", () => {
     expect(selection.selectedColumnIndexes.value).toEqual(new Set([0, 1, 2]));
   });
 
+  it("distinguishes a column merely covered by a wider full-height range from one exclusively selected", () => {
+    const selection = createSelection();
+
+    // Full-height rectangle spanning columns 1-2 (e.g. dragged across two columns).
+    selection.selectSingleCell(0, 1);
+    selection.extendCellSelectionTo(3, 2);
+
+    expect(selection.columnIsSelected(1)).toBe(true);
+    expect(selection.columnIsSelected(2)).toBe(true);
+    expect(selection.columnIsExclusivelySelected(1)).toBe(false);
+    expect(selection.columnIsExclusivelySelected(2)).toBe(false);
+
+    // Narrowing to just column 1 (what a header click/selectColumn does) makes it exclusive.
+    selection.selectColumn(1);
+
+    expect(selection.columnIsExclusivelySelected(1)).toBe(true);
+    expect(selection.columnIsExclusivelySelected(2)).toBe(false);
+  });
+
+  it("treats an explicit multi-column header selection as exclusive for every column it contains", () => {
+    const selection = createSelection();
+
+    // Deliberate multi-column selection via header click + shift-click (not a stray cell range).
+    selection.selectColumn(0);
+    selection.selectColumn(1, rowEvent({ shift: true }));
+
+    expect(selection.hasColumnSelection.value).toBe(true);
+    expect(selection.columnIsExclusivelySelected(0)).toBe(true);
+    expect(selection.columnIsExclusivelySelected(1)).toBe(true);
+    expect(selection.columnIsExclusivelySelected(2)).toBe(false);
+  });
+
   it("moves a single-column rectangular cell selection with its column after reordering", () => {
     const selection = createSelection();
 

apps/desktop/src/composables/useDataGridSelection.ts

@@ -694,6 +694,18 @@ export function useDataGridSelection(options: UseDataGridSelectionOptions) {
     return range.startCol <= colIndex && range.endCol >= colIndex && range.startRow === 0 && range.endRow >= displayItems.value.length - 1;
   }
 
+  // Unlike columnIsSelected (used for header highlighting, where any column touched by a
+  // wider selection should light up), this requires the selected cell RANGE to cover this
+  // column only. An explicit multi-column header selection (hasColumnSelection) is left as-is:
+  // that's a deliberate user gesture (click/shift-click/ctrl-click headers), not a stray
+  // full-height cell range left over from selecting a block in the grid body.
+  function columnIsExclusivelySelected(colIndex: number): boolean {
+    if (hasColumnSelection.value) return selectedColumnIndexes.value.has(colIndex);
+    const range = selectedRange.value;
+    if (!range) return false;
+    return range.startCol === colIndex && range.endCol === colIndex && range.startRow === 0 && range.endRow >= displayItems.value.length - 1;
+  }
+
   function selectedRangeStart(): CellPosition | null {
     const range = selectedRange.value;
     if (!range) return null;
@@ -727,6 +739,7 @@ export function useDataGridSelection(options: UseDataGridSelectionOptions) {
     isCellSelectionDragConfirmed,
     cellIsSelected,
     columnIsSelected,
+    columnIsExclusivelySelected,
     selectedRangeStart,
     selectedRowIds,
     selectedColumnIndexes,