docs(galaxy): rewrite stale PR-4.W/legacy-host forward-ref comments to shipped reality (#13)

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Galaxy/GalaxyDriver.cs

@@ -49,11 +49,11 @@ public sealed class GalaxyDriver
     private IGalaxyHierarchySource? _hierarchySource;
     private GalaxyRepositoryClient? _ownedRepositoryClient;
 
-    // PR 4.2 — IGalaxyDataReader is the test seam for IReadable. PR 4.4 supplies the
-    // production implementation that wraps GalaxyMxSession's SubscribeBulk + StreamEvents
-    // pump; until then ReadAsync throws NotSupportedException when the reader is null
-    // (legacy-host backend handles reads in production via DriverNodeManager's
-    // capability-routing).
+    // IGalaxyDataReader is the test seam for IReadable. Production ReadAsync calls
+    // ReadViaSubscribeOnceAsync (SubscribeBulk + first-event wait + Unsubscribe) through
+    // the live GalaxyMxSession built by InitializeAsync; no legacy-host backend exists.
+    // When a test injects a reader via the internal ctor, that injected reader is used
+    // instead so capability flow can be exercised without a real gRPC round-trip.
     private IGalaxyDataReader? _dataReader;
 
     // PR 4.3 — IGalaxyDataWriter is the test seam for IWritable. Production wraps
@@ -90,9 +90,10 @@ public sealed class GalaxyDriver
     // handles are added/removed (Driver.Galaxy-006 fix: HashSet.First() is unstable).
     private readonly List<GalaxyAlarmSubscriptionHandle> _alarmSubscriptions = new();
 
-    // PR 4.W — production runtime owned by InitializeAsync. The driver builds these
-    // when it opens a real gw session; tests bypass them by injecting seams via the
-    // internal ctor.
+    // Production runtime owned by InitializeAsync (BuildProductionRuntimeAsync). The
+    // driver builds these when it opens a real gw session; tests bypass them by
+    // injecting seams via the internal ctor, which leaves both fields null and skips
+    // BuildProductionRuntimeAsync entirely.
     private GalaxyMxSession? _ownedMxSession;
     private MxGatewayClient? _ownedMxClient;
 
@@ -666,9 +667,10 @@ public sealed class GalaxyDriver
         ObjectDisposedException.ThrowIf(_disposed, this);
         ArgumentNullException.ThrowIfNull(builder);
 
-        // PR 4.3 — capture SecurityClassification per attribute. PR 4.W — also refresh
-        // the per-platform probe watcher's membership after discovery so newly-added
-        // $WinPlatform / $AppEngine objects start advising their ScanState attribute.
+        // Wrap the builder with a SecurityCapturingBuilder so each discovered attribute's
+        // SecurityClassification is recorded in _securityByFullRef for write-time routing.
+        // After discovery, SyncPlatformsAsync refreshes the probe watcher's membership so
+        // newly added $WinPlatform / $AppEngine objects start advising their ScanState attribute.
         var capturingBuilder = new SecurityCapturingBuilder(builder, _securityByFullRef);
         var source = _hierarchySource ??= BuildDefaultHierarchySource();
         var discoverer = new GalaxyDiscoverer(source);