Merge hw4-udtwrite (#592/#611)

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

# Conflicts:
#	docs/drivers/AbCip.md

CLAUDE.md

@@ -1098,7 +1098,11 @@ re-emit a concrete default. The defaults differ per driver (final review, 2026-1
 Refusals are not comms faults: an Unsupported refusal (`BadNotSupported`) and an AbCip native **type
 mismatch** (`BadTypeMismatch`, where libplctag returned Good garbage for a same-width mis-authored type) both
 keep the tag handle, leave driver health alone (no `Degraded`, nothing for the comms-loss watchdog) and warn
-once per tag — only genuine transport failures evict and degrade. `DeviceSessionPool.Shared` logs through the
+once per tag — only genuine transport failures evict and degrade (a runtime `NotSupportedException` too, #611 —
+it used to latch `Degraded`). AbCip width-checks every scalar **write** against the controller's bytes before
+sending, on both transports (#611; libplctag used to patch part of its buffer and send it all). Controller-discovered
+UDT members are writable once browse-committed and authored `ReadWrite` (BIT members included — the controller
+applies the bit) — ab_server-proven only, member and BIT-member writes are unverified on real hardware; whole-UDT writes are refused `BadNotSupported` by decision (`docs/drivers/AbCip.md` §Member writes). `DeviceSessionPool.Shared` logs through the
 host logger factory (wired in `DriverFactoryBootstrap`; the FOCAS and TwinCAT factories' `Register(registry, ILoggerFactory?)` take one too, #602 CONV-3). The AbCip `browsePageDelayMs` knob has an AdminUI field (`AbCipDriverForm` "Browse page delay (ms)"). libplctag is confined to `Libplctag*.cs` adapters by
 `LibplctagConfinementGuardTests`; do not reference it elsewhere. See `docs/drivers/AbCip.md` §Transport,
 `docs/drivers/AbLegacy.md` §Transport + §Wire evidence, `docs/Configuration.md` §`Drivers:AbCip`, and