feat(frontend): toCSV + csvFilename for data export

frontend/tests/dataExport.test.js

@@ -125,3 +125,33 @@ describe('buildMatrix', () => {
     expect(m.columns.length).toBe(2);
   });
 });
+
+import { toCSV, csvFilename } from '../src/lib/dataExport';
+
+describe('toCSV', () => {
+  it('writes a header row of Date + column headers, then data rows', () => {
+    const matrix = {
+      columns: [{ id: 'a1', header: 'Alpha' }, { id: 'a2', header: 'Beta' }],
+      rows: [{ date: '2026-07-01', values: [5, ''] }, { date: '2026-07-02', values: ['', 9] }],
+    };
+    expect(toCSV(matrix)).toBe('Date,Alpha,Beta\n2026-07-01,5,\n2026-07-02,,9');
+  });
+  it('escapes commas, quotes, and newlines per RFC 4180', () => {
+    const matrix = {
+      columns: [{ id: 'a1', header: 'Note, field' }],
+      rows: [{ date: '2026-07-01', values: ['he said "hi"'] }, { date: '2026-07-02', values: ['line1\nline2'] }],
+    };
+    expect(toCSV(matrix)).toBe(
+      'Date,"Note, field"\n2026-07-01,"he said ""hi"""\n2026-07-02,"line1\nline2"',
+    );
+  });
+});
+
+describe('csvFilename', () => {
+  it('slugifies the experiment title and parameter label', () => {
+    expect(csvFilename('My Study #1', 'Success rate')).toBe('My-Study-1-Success-rate.csv');
+  });
+  it('falls back to "export" when both slugs are empty', () => {
+    expect(csvFilename('', '')).toBe('export.csv');
+  });
+});