fix(frontend/csvParser): accept single-column CSVs without a detectable delimiter

frontend/__tests__/csvParser.test.ts

@@ -59,4 +59,17 @@ describe('parseCSV', () => {
     expect(result.headers).toEqual(['a', 'b', 'c']);
     expect(result.rows).toEqual([]);
   });
+
+  it('parses a single-column CSV (no delimiter character anywhere)', async () => {
+    // Mirrors test_symbols_failed.csv: header + tickers, CRLF line endings,
+    // no commas/tabs/pipes/semicolons. PapaParse can't auto-detect a delimiter
+    // and emits an "UndetectableDelimiter" warning; the data still parses fine.
+    const csv = 'Symbol\r\nAMZN\r\nCRSR\r\nAMD\r\nMSFT\r\n0700.HK\r\n';
+    const result = await parseCSV(fileFromString(csv));
+
+    expect(result.headers).toEqual(['Symbol']);
+    expect(result.rows).toHaveLength(5);
+    expect(result.rows[0]).toEqual({ Symbol: 'AMZN' });
+    expect(result.rows[4]).toEqual({ Symbol: '0700.HK' });
+  });
 });

frontend/lib/csvParser.ts

@@ -8,8 +8,15 @@ export const parseCSV = (file: File): Promise<CsvData> => {
       dynamicTyping: true,
       skipEmptyLines: true,
       complete: (results) => {
-        if (results.errors.length > 0) {
-          reject(new Error(results.errors[0].message));
+        // PapaParse emits a non-fatal "UndetectableDelimiter" warning when the
+        // sample contains none of `,` `\t` `|` `;` (e.g. a single-column CSV).
+        // The data still parses correctly using the default `,` delimiter,
+        // so this warning is informational — drop it before deciding to reject.
+        const fatalErrors = results.errors.filter(
+          (e) => !(e.type === 'Delimiter' && e.code === 'UndetectableDelimiter')
+        );
+        if (fatalErrors.length > 0) {
+          reject(new Error(fatalErrors[0].message));
           return;
         }