Change SessionFsSqliteResult.Rows to IList<object?[]> and LastInsertRowid to long?

Rows are now positional arrays aligned with the Columns list, avoiding
redundant dictionary key construction. The bridge code converts to keyed
dictionaries for the wire format. LastInsertRowid changed from double?
to long? since SQLite row IDs are always integers.

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

Author: SteveSandersonMS

dotnet/src/SessionFsProvider.cs

@@ -16,14 +16,14 @@ public class SessionFsSqliteResult
     /// <summary>Column names from the result set.</summary>
     public IList<string> Columns { get; set; } = [];
 
-    /// <summary>For SELECT: array of row objects. For others: empty array.</summary>
-    public IList<IDictionary<string, object>> Rows { get; set; } = [];
+    /// <summary>For SELECT: rows as positional arrays aligned with <see cref="Columns"/>. For others: empty.</summary>
+    public IList<object?[]> Rows { get; set; } = [];
 
     /// <summary>Number of rows affected (for INSERT/UPDATE/DELETE).</summary>
     public long RowsAffected { get; set; }
 
     /// <summary>Last inserted row ID (for INSERT).</summary>
-    public double? LastInsertRowid { get; set; }
+    public long? LastInsertRowid { get; set; }
 }
 
 /// <summary>
@@ -288,10 +288,25 @@ async Task<SessionFsSqliteQueryResult> ISessionFsHandler.SqliteQueryAsync(Sessio
         try
         {
             var result = await sqliteProvider.QueryAsync(request.QueryType, request.Query, request.Params, cancellationToken).ConfigureAwait(false);
+            var columns = result?.Columns ?? [];
+            var rows = result?.Rows ?? [];
+
+            // Convert positional arrays to keyed dictionaries for the wire format.
+            var keyedRows = new List<IDictionary<string, object>>(rows.Count);
+            foreach (var row in rows)
+            {
+                var dict = new Dictionary<string, object>(columns.Count);
+                for (var i = 0; i < columns.Count && i < row.Length; i++)
+                {
+                    dict[columns[i]] = row[i]!;
+                }
+                keyedRows.Add(dict);
+            }
+
             return new SessionFsSqliteQueryResult
             {
-                Rows = result?.Rows ?? [],
-                Columns = result?.Columns ?? [],
+                Rows = keyedRows,
+                Columns = columns,
                 RowsAffected = result?.RowsAffected ?? 0,
                 LastInsertRowid = result?.LastInsertRowid,
             };

dotnet/test/E2E/InMemorySessionFsSqliteHandler.cs

@@ -77,13 +77,13 @@ private SqliteConnection GetOrCreateDb()
                 columns.Add(reader.GetName(i));
             }
 
-            var rows = new List<IDictionary<string, object>>();
+            var rows = new List<object?[]>();
             while (reader.Read())
             {
-                var row = new Dictionary<string, object>();
+                var row = new object?[reader.FieldCount];
                 for (var i = 0; i < reader.FieldCount; i++)
                 {
-                    row[reader.GetName(i)] = reader.IsDBNull(i) ? null! : reader.GetValue(i);
+                    row[i] = reader.IsDBNull(i) ? null : reader.GetValue(i);
                 }
                 rows.Add(row);
             }