Add XML docs

YesNt.Interpreter/Runtime/Line.cs

@@ -1,10 +1,16 @@
 namespace YesNt.Interpreter.Runtime;
 
+/// <summary>
+/// Represents a single source line together with its location metadata.
+/// </summary>
 internal class Line(string content, string fileName, int lineNumber)
 {
+    /// <summary>Gets or sets the raw text content of the line.</summary>
     public string Content { get; set; } = content;
 
+    /// <summary>Gets or sets the name of the source file this line originated from.</summary>
     public string FileName { get; set; } = fileName;
 
+    /// <summary>Gets or sets the zero-based line index within <see cref="FileName"/>.</summary>
     public int LineNumber { get; set; } = lineNumber;
 }