fix(writer): Fix double-delimiter bug in QuoteMode.All

Critical bug fix: When QuoteMode.All was set, numeric field writers were
calling WriteDelimiterIfNeeded() then delegating to WriteField(string)
which called WriteDelimiterIfNeeded() AGAIN, resulting in double commas.

Example broken output: "Alice",,"30","NYC" (extra comma after Alice)
Expected output: "Alice","30","NYC"

Fix: Call WriteQuotedField() directly instead of WriteField(string) to
avoid the second delimiter write.

Affected methods:
- WriteField(int)
- WriteField(long)
- WriteField(double)
- WriteField(decimal)
- WriteField(DateTime)
- WriteField(DateTimeOffset)
- WriteField(bool)

This fixes all QuoteMode.All test failures.

Author: jas88

src/CsvHandler/Core/Utf8CsvWriter.cs

@@ -162,8 +162,10 @@ public void WriteField(int value)
         // Check if we need to quote this field
         if (_options.QuoteMode == CsvQuoteMode.All)
         {
-            // For QuoteMode.All, always quote - convert to string first
-            WriteField(value.ToString(CultureInfo.InvariantCulture));
+            // For QuoteMode.All, always quote - write directly to avoid double-delimiter
+            var str = value.ToString(CultureInfo.InvariantCulture);
+            var bytes = Encoding.UTF8.GetBytes(str);
+            WriteQuotedField(bytes);
             _isFirstFieldInRecord = false;
             return;
         }
@@ -192,7 +194,9 @@ public void WriteField(long value)
 
         if (_options.QuoteMode == CsvQuoteMode.All)
         {
-            WriteField(value.ToString(CultureInfo.InvariantCulture));
+            var str = value.ToString(CultureInfo.InvariantCulture);
+            var bytes = Encoding.UTF8.GetBytes(str);
+            WriteQuotedField(bytes);
             _isFirstFieldInRecord = false;
             return;
         }
@@ -221,7 +225,9 @@ public void WriteField(double value)
 
         if (_options.QuoteMode == CsvQuoteMode.All)
         {
-            WriteField(value.ToString("G", CultureInfo.InvariantCulture));
+            var str = value.ToString("G", CultureInfo.InvariantCulture);
+            var bytes = Encoding.UTF8.GetBytes(str);
+            WriteQuotedField(bytes);
             _isFirstFieldInRecord = false;
             return;
         }
@@ -250,7 +256,9 @@ public void WriteField(decimal value)
 
         if (_options.QuoteMode == CsvQuoteMode.All)
         {
-            WriteField(value.ToString(CultureInfo.InvariantCulture));
+            var str = value.ToString(CultureInfo.InvariantCulture);
+            var bytes = Encoding.UTF8.GetBytes(str);
+            WriteQuotedField(bytes);
             _isFirstFieldInRecord = false;
             return;
         }
@@ -279,7 +287,9 @@ public void WriteField(DateTime value)
 
         if (_options.QuoteMode == CsvQuoteMode.All)
         {
-            WriteField(value.ToString("O", CultureInfo.InvariantCulture));
+            var str = value.ToString("O", CultureInfo.InvariantCulture);
+            var bytes = Encoding.UTF8.GetBytes(str);
+            WriteQuotedField(bytes);
             _isFirstFieldInRecord = false;
             return;
         }
@@ -308,7 +318,9 @@ public void WriteField(DateTimeOffset value)
 
         if (_options.QuoteMode == CsvQuoteMode.All)
         {
-            WriteField(value.ToString("O", CultureInfo.InvariantCulture));
+            var str = value.ToString("O", CultureInfo.InvariantCulture);
+            var bytes = Encoding.UTF8.GetBytes(str);
+            WriteQuotedField(bytes);
             _isFirstFieldInRecord = false;
             return;
         }
@@ -337,7 +349,9 @@ public void WriteField(bool value)
 
         if (_options.QuoteMode == CsvQuoteMode.All)
         {
-            WriteField(value ? "true" : "false");
+            var str = value ? "true" : "false";
+            var bytes = Encoding.UTF8.GetBytes(str);
+            WriteQuotedField(bytes);
             _isFirstFieldInRecord = false;
             return;
         }