feat: add onProgress callback to FillDataTableAsync

Optional Action<int> called on the UI thread after each batch
with the running total of rows loaded. Useful for label/title
updates and diagnosing large result set loading.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: vkuttyp

src/SqlDotnetty.Core/ISqlDatabase.cs

@@ -173,20 +173,25 @@ public static System.Data.DataRow ToDataRow(this SqlRow row)
     /// <param name="rows">The async row stream from <c>QueryStreamAsync</c>.</param>
     /// <param name="table">A DataTable already bound to a DataGridView (or similar).</param>
     /// <param name="batchSize">Rows to accumulate before flushing to the DataTable. Default 500.</param>
+    /// <param name="onProgress">
+    /// Optional callback invoked on the UI thread after each batch is flushed.
+    /// Receives the total number of rows added so far. Use to update a label, progress bar, etc.
+    /// </param>
     /// <param name="ct">Cancellation token.</param>
     /// <example>
     /// <code>
     /// var dt = new DataTable();
-    /// dataGridView1.DataSource = dt;          // bind upfront
+    /// dataGridView1.DataSource = dt;
     ///
     /// await conn.QueryStreamAsync("SELECT * FROM BigTable")
-    ///           .FillDataTableAsync(dt);       // rows appear in batches, form stays responsive
+    ///           .FillDataTableAsync(dt, onProgress: n => label1.Text = $"{n} rows loaded");
     /// </code>
     /// </example>
     public static async Task FillDataTableAsync(
         this IAsyncEnumerable<SqlRow> rows,
         System.Data.DataTable table,
         int batchSize = 500,
+        Action<int>? onProgress = null,
         CancellationToken ct = default)
     {
         // Bounded channel: producer (background) reads network; consumer (UI thread) flushes batches.
@@ -225,9 +230,12 @@ public static async Task FillDataTableAsync(
 
         // Consumer: runs on the calling (UI) thread — no ConfigureAwait(false).
         // await Task.Yield() between batches lets the message pump process redraws/clicks.
+        int totalRows = 0;
         await foreach (var batch in channel.Reader.ReadAllAsync(ct))
         {
             FlushBatch(table, batch);
+            totalRows += batch.Count;
+            onProgress?.Invoke(totalRows);
             await Task.Yield();
         }