feat(ui): add customizable download table columns

Add persisted column reordering, positional alignment, animated drag feedback, and resize cleanup for the download table. Keep row actions at the trailing edge, preserve RTL/LTR behavior, and include localized column controls and sidebar alignment fixes.

src/utils/downloadTableColumns.test.ts

@@ -0,0 +1,53 @@
+import { describe, expect, it } from 'vitest';
+import {
+  DEFAULT_COLUMN_ALIGNMENTS,
+  DEFAULT_COLUMN_ORDER,
+  normalizeColumnAlignments,
+  normalizeColumnOrder,
+  normalizeColumnWidths,
+} from './downloadTableColumns';
+
+describe('download table column preferences', () => {
+  it('normalizes a persisted order without losing or duplicating columns', () => {
+    expect(normalizeColumnOrder(['Status', 'Status', 'not-a-column', 'File Name'])).toEqual([
+      'Status',
+      'File Name',
+      'Size',
+      'Speed',
+      'ETA',
+      'Date Added',
+    ]);
+  });
+
+  it('clamps persisted widths to column minimums and restores malformed entries', () => {
+    expect(normalizeColumnWidths([10, 70, Number.POSITIVE_INFINITY, 80, '48', 140])).toEqual([
+      160,
+      70,
+      220,
+      80,
+      80,
+      140,
+    ]);
+
+    expect(normalizeColumnWidths([0, 100, 220, 100, 80, 170])[0]).toBe(160);
+  });
+
+  it('keeps only supported positional alignment values', () => {
+    expect(normalizeColumnAlignments({
+      'File Name': 'center',
+      Size: 'right',
+      Status: 'invalid',
+      Speed: 'left',
+    })).toEqual({
+      ...DEFAULT_COLUMN_ALIGNMENTS,
+      'File Name': 'center',
+      Size: 'right',
+      Speed: 'left',
+    });
+  });
+
+  it('restores the default order for malformed persisted data', () => {
+    expect(normalizeColumnOrder(null)).toEqual([...DEFAULT_COLUMN_ORDER]);
+    expect(normalizeColumnAlignments(null)).toEqual(DEFAULT_COLUMN_ALIGNMENTS);
+  });
+});