feat(lmxproxy): phase 5 — client core (ILmxProxyClient, connection, read/write/subscribe)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

lmxproxy/src/ZB.MOM.WW.LmxProxy.Client/Domain/QualityExtensions.cs

@@ -11,4 +11,19 @@ public static class QualityExtensions
 
     /// <summary>Returns true if quality is in the Bad family (byte < 64).</summary>
     public static bool IsBad(this Quality q) => (byte)q < 64;
+
+    /// <summary>
+    /// Converts an OPC UA 32-bit status code to the simplified <see cref="Quality"/> enum.
+    /// Uses the top two bits to determine the quality family.
+    /// </summary>
+    public static Quality FromStatusCode(uint statusCode)
+    {
+        uint category = statusCode & 0xC0000000;
+        return category switch
+        {
+            0x00000000 => Quality.Good,
+            0x40000000 => Quality.Uncertain,
+            _ => Quality.Bad
+        };
+    }
 }