fix(ab): a refused operation is BadNotSupported, not a comms fault (Task 22 review r1; closes #571)

Native is the default, so a locally refused write must not look like a comms fault.

- AbLegacy: an AbTransportException with AbStatus.Unsupported (status-bit sub-element writes, PLC-5
  non-N reads, all PLC-5 writes; libplctag's ErrorUnsupported maps here too) now returns
  BadNotSupported on both the read and the write path (incl. the bit-RMW path). The tag handle is
  not evicted and driver health is not touched. A native runtime whose init read is refused locally
  is CACHED rather than disposed, so a poll of a refused tag does not re-create (and re-lease the
  pooled connection) every cycle.
- AbCip: the same mapping on the write path and both read paths (single + whole-UDT).
- Uses the existing named BadNotSupported constants (StatusCodeParityTests guard).
- Tests (falsified by disabling the mapping, and separately the keep-on-refusal): status-bit
  writes and PLC-5 read/write through the driver over the native runtime — BadNotSupported, zero
  wire requests, one create, health unchanged; AbCip refused read/write via a refusing fake plus a
  control that a non-refusal failure still evicts and degrades.
- Docs/CLAUDE.md: BadNotSupported; #571 known-gap wording removed.

Claude-Session: https://claude.ai/code/session_01Ef2ozxS7QPanGT8uoATbTe

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.AbCip/AbCipDriver.cs

@@ -854,6 +854,13 @@ public sealed class AbCipDriver : IDriver, IReadable, IWritable, ITagDiscovery,
         {
             throw;
         }
+        catch (AbTransportException ate) when (ate.Status == AbStatus.Unsupported)
+        {
+            // A deterministic local refusal — not a comms fault: BadNotSupported, keep the handle, no
+            // health signal (Task 22 review r1).
+            results[fb.OriginalIndex] = new DataValueSnapshot(null, AbCipStatusMapper.BadNotSupported, null, now);
+            return ReadOutcome.None;
+        }
         catch (Exception ex)
         {
             // Transport exception — evict so the next read creates a fresh handle. An AbTransportException
@@ -928,6 +935,11 @@ public sealed class AbCipDriver : IDriver, IReadable, IWritable, ITagDiscovery,
         {
             throw;
         }
+        catch (AbTransportException ate) when (ate.Status == AbStatus.Unsupported)
+        {
+            StampGroupStatus(group, results, now, AbCipStatusMapper.BadNotSupported);
+            return ReadOutcome.None;
+        }
         catch (Exception ex)
         {
             EvictRuntime(device, parent.Name);
@@ -1064,6 +1076,15 @@ public sealed class AbCipDriver : IDriver, IReadable, IWritable, ITagDiscovery,
                     "AbCip write value out of range for tag {Tag} on device {Device}",
                     w.FullReference, def.DeviceHostAddress);
             }
+            catch (AbTransportException ate) when (ate.Status == AbStatus.Unsupported)
+            {
+                // A deterministic local refusal (e.g. the native runtime cannot type the write) — not a comms
+                // fault: BadNotSupported, keep the handle, leave health alone (Task 22 review r1).
+                results[i] = new WriteResult(AbCipStatusMapper.BadNotSupported);
+                _logger.LogWarning(ate,
+                    "AbCip write refused (not supported) for tag {Tag} on device {Device}",
+                    w.FullReference, def.DeviceHostAddress);
+            }
             catch (Exception ex)
             {
                 // Transport / wire error — evict so the next write creates a fresh handle.