fix(DbExporter): fix compressed size calculation and clean up

- Move file size read after streams are disposed to get accurate compressed size
- Clean up definition files to use working example queries
- Add .gitignore for output directory

Tools/DbExporter/DatabaseExporter.cs

@@ -29,30 +29,36 @@ public sealed class DatabaseExporter
         await using var baseReader = await command.ExecuteReaderAsync(cancellationToken);
         var reader = new CountingDataReader(baseReader);
 
-        long uncompressedSize = 0;
+        long uncompressedSize;
+        string hash;
+        int rowCount;
 
         // Use a counting stream wrapper to track uncompressed bytes
-        using var sha256 = SHA256.Create();
-        await using var outputFile = new FileStream(definition.OutputPath, FileMode.Create, FileAccess.Write, FileShare.None, 256 * 1024);
-        await using var compressStream = new CompressionStream(outputFile, definition.CompressionLevel);
-        await using var countingStream = new CountingStream(compressStream);
-        await using var hashStream = new CryptoStream(countingStream, sha256, CryptoStreamMode.Write);
+        using (var sha256 = SHA256.Create())
+        {
+            await using var outputFile = new FileStream(definition.OutputPath, FileMode.Create, FileAccess.Write, FileShare.None, 256 * 1024);
+            await using var compressStream = new CompressionStream(outputFile, definition.CompressionLevel);
+            await using var countingStream = new CountingStream(compressStream);
+            await using var hashStream = new CryptoStream(countingStream, sha256, CryptoStreamMode.Write);
 
-        // Serialize to protobuf
-        DataSerializer.Serialize(hashStream, reader);
+            // Serialize to protobuf
+            DataSerializer.Serialize(hashStream, reader);
 
-        hashStream.FlushFinalBlock();
-        uncompressedSize = countingStream.BytesWritten;
+            hashStream.FlushFinalBlock();
+            uncompressedSize = countingStream.BytesWritten;
+            rowCount = reader.RowCount;
 
-        var hash = Convert.ToHexString(sha256.Hash!).ToLowerInvariant();
+            hash = Convert.ToHexString(sha256.Hash!).ToLowerInvariant();
+        } // All streams disposed here, file fully written
 
         // Write sidecar hash file
         var hashFilePath = definition.OutputPath + ".sha256";
         await File.WriteAllTextAsync(hashFilePath, hash, cancellationToken);
 
+        // Read file size after streams are closed
         var compressedSize = new FileInfo(definition.OutputPath).Length;
 
-        return new ExportResult(reader.RowCount, uncompressedSize, compressedSize, hash);
+        return new ExportResult(rowCount, uncompressedSize, compressedSize, hash);
     }
 
     private static DbConnection CreateConnection(string providerType, string connectionString)