fix(twincat): read-singly fallback for any non-comms overall sum error, once-per-device warning, wording (#645 re-review)

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

docs/drivers/TwinCAT.md

@@ -208,11 +208,12 @@ command is unverified, hence opt-in.
   without joining the batch; a bit-indexed BOOL and a handle-addressed symbol (`0xF005`) are read singly.
 - Per-item ADS error codes map to that tag only (`MapAdsError`); a response shorter than asked is a size error
   for that item, not a failed chunk. The overall code is the command's.
-- **Latch vs split.** Only overall ADS **1793 / 1794** (service / index group not supported) throws
+- **Latch vs read-singly.** Only overall ADS **1793 / 1794** (service / index group not supported) throws
   `TwinCATSumReadRefusedException`; the driver logs once, marks the device `SumReadUnsupported` and reads
-  singly until re-initialise. **1792 / 1797 / 1798** (general error, bad size, bad data) mean *this request*
-  was rejected — typically too big — so that chunk is read singly for this poll and nothing is latched. A
-  comms-level failure is neither: that chunk goes `BadCommunicationError` and the next poll tries again.
+  singly until re-initialise. **Any other non-comms overall code** (1792 general error, 1795 offset, 1797 size, 1798 data, ...) means
+  *this request* was rejected — typically too big — so that chunk is read singly for this poll, nothing is
+  latched, and a Warning is logged once per device so the live gate can see sum-read is not working there. A
+  comms-level failure (router / port / timeout) is neither: that chunk goes `BadCommunicationError` and the next poll tries again.
 - A one-item chunk is just a single read. Sum-**write** is not implemented (writes stay per-tag).
 
 ### `/hosts` diagnostics (`IDriverDiagnostics`, opt-in)