docs(opcua): note FB-7 surgical-shape reach (stable-FullName drivers only)

Live-verify finding: the surgical DataType/array path only fires for drivers whose
TagConfig carries a stable top-level FullName (Galaxy/OpcUaClient). For protocol
drivers (Modbus/S7/...), ExtractTagFullName falls back to the raw TagConfig blob, so
a shape edit also mutates FullName → safe full-rebuild fallback. Comment-only.

src/Server/ZB.MOM.WW.OtOpcUa.OpcUaServer/AddressSpaceApplier.cs

@@ -401,6 +401,12 @@ public sealed class AddressSpaceApplier
     // differences still fall through to a rebuild — FullName/DriverInstanceId re-route the node to a different
     // driver point, Name re-derives the NodeId, and an alarm flip turns the node into a Part 9 condition. The
     // override-unequal default also covers any future field.
+    // REACH (live-verified FB-7): the shape path only fires for drivers whose TagConfig carries a stable
+    // top-level "FullName" (Galaxy = tag_name.AttributeName; OpcUaClient = the node id) — there a DataType/array
+    // edit leaves FullName untouched ⇒ surgical. For structured-TagConfig protocol drivers (Modbus/S7/AbCip/…)
+    // AddressSpaceComposer.ExtractTagFullName falls back to the RAW TagConfig blob as FullName, so a DataType/
+    // array edit also mutates that blob ⇒ FullName differs ⇒ this returns false ⇒ full rebuild. That is the
+    // correct safe default (a protocol driver's subscription needs re-spawning for a new shape anyway).
     private static bool TagDeltaIsSurgicalEligible(AddressSpacePlan.EquipmentTagDelta d) =>
         d.Previous.Alarm is null && d.Current.Alarm is null &&
         (d.Previous with