Expand XML docs across bridge and test code

src/ZB.MOM.WW.LmxOpcUa.Host/Domain/Vtq.cs

@@ -7,10 +7,27 @@ namespace ZB.MOM.WW.LmxOpcUa.Host.Domain
     /// </summary>
     public readonly struct Vtq : IEquatable<Vtq>
     {
+        /// <summary>
+        /// Gets the runtime value returned for the Galaxy attribute.
+        /// </summary>
         public object? Value { get; }
+
+        /// <summary>
+        /// Gets the timestamp associated with the runtime value.
+        /// </summary>
         public DateTime Timestamp { get; }
+
+        /// <summary>
+        /// Gets the quality classification that tells OPC UA clients whether the value is usable.
+        /// </summary>
         public Quality Quality { get; }
 
+        /// <summary>
+        /// Initializes a new instance of the <see cref="Vtq"/> struct for a Galaxy attribute value.
+        /// </summary>
+        /// <param name="value">The runtime value returned by MXAccess.</param>
+        /// <param name="timestamp">The timestamp assigned to the runtime value.</param>
+        /// <param name="quality">The quality classification for the runtime value.</param>
         public Vtq(object? value, DateTime timestamp, Quality quality)
         {
             Value = value;
@@ -18,15 +35,42 @@ namespace ZB.MOM.WW.LmxOpcUa.Host.Domain
             Quality = quality;
         }
 
+        /// <summary>
+        /// Creates a good-quality VTQ snapshot for a successfully read or subscribed attribute value.
+        /// </summary>
+        /// <param name="value">The runtime value to wrap.</param>
+        /// <returns>A VTQ carrying the provided value with the current UTC timestamp and good quality.</returns>
         public static Vtq Good(object? value) => new Vtq(value, DateTime.UtcNow, Quality.Good);
+
+        /// <summary>
+        /// Creates a bad-quality VTQ snapshot when no usable runtime value is available.
+        /// </summary>
+        /// <param name="quality">The specific bad quality reason to expose to clients.</param>
+        /// <returns>A VTQ with no value, the current UTC timestamp, and the requested bad quality.</returns>
         public static Vtq Bad(Quality quality = Quality.Bad) => new Vtq(null, DateTime.UtcNow, quality);
+
+        /// <summary>
+        /// Creates an uncertain VTQ snapshot when the runtime value exists but should be treated cautiously.
+        /// </summary>
+        /// <param name="value">The runtime value to wrap.</param>
+        /// <returns>A VTQ carrying the provided value with the current UTC timestamp and uncertain quality.</returns>
         public static Vtq Uncertain(object? value) => new Vtq(value, DateTime.UtcNow, Quality.Uncertain);
 
+        /// <summary>
+        /// Compares two VTQ snapshots for exact value, timestamp, and quality equality.
+        /// </summary>
+        /// <param name="other">The other VTQ snapshot to compare.</param>
+        /// <returns><see langword="true"/> when all fields match; otherwise, <see langword="false"/>.</returns>
         public bool Equals(Vtq other) =>
             Equals(Value, other.Value) && Timestamp == other.Timestamp && Quality == other.Quality;
 
+        /// <inheritdoc />
         public override bool Equals(object? obj) => obj is Vtq other && Equals(other);
+
+        /// <inheritdoc />
         public override int GetHashCode() => HashCode.Combine(Value, Timestamp, Quality);
+
+        /// <inheritdoc />
         public override string ToString() => $"Vtq({Value}, {Timestamp:O}, {Quality})";
     }
 }