fix(dcl): MxGateway adapter treats a graceful end of the event stream as a disconnect — a dashboard 'close session' (or graceful gateway shutdown) completes the stream with OK, leaving the adapter Connected on a dead session: values frozen at last GOOD quality, every write 'Session … was not found' until restart (QA vq03 Z28061 MoveIn, 2026-08-20). Pinned: signals once while connected, silent for superseded loops / own teardown

docs/requirements/Component-DataConnectionLayer.md

@@ -80,7 +80,7 @@ All protocols produce the same value tuple consumed by Instance Actors. Before t
 - Session-based: `OpenSession` + `Register` on connect; `AddItem` + `Advise` per subscription; value changes arrive on the gateway's server-streaming event feed (`StreamEvents`), resumable via `worker_sequence`.
 - Read/Write via `ReadBulk` / `WriteBulk`; writes carry a configurable `WriteUserId`. Quality maps the OPC-style quality byte (≥192 Good, ≥64 Uncertain, else Bad), with a failing MXAccess status proxy treated as Bad.
 - Galaxy hierarchy browse via the separate `GalaxyRepositoryClient` — objects are navigable nodes (keyed by Galaxy gobject id), attributes are selectable leaves (keyed by full tag reference). Browse is **lazy and attribute-light**: navigation uses `BrowseChildren` with `include_attributes=false` (child objects only), and an object's own attributes are fetched only when it is expanded, via `DiscoverHierarchy(root=<object>, max_depth=0)` scoped to that single object. This keeps each browse level's reply small; inlining every child's full attribute set could exceed the Akka remote frame and silently drop the reply.
-- Disconnect detection: a fault on the event stream raises `IDataConnection.Disconnected`, driving the same reconnection state machine as OPC UA.
+- Disconnect detection: a fault on the event stream raises `IDataConnection.Disconnected`, driving the same reconnection state machine as OPC UA. **A graceful (OK-status) end of the event stream while the adapter did not cancel it is ALSO a disconnect** (fix 2026-08-20): the gateway completes a session's subscriber channels with no error when the session is closed from its dashboard or on a graceful gateway shutdown (`CompleteAllSubscribers(error: null)`), so before the fix `RunEventLoopAsync` simply returned, the adapter stayed `Connected`, subscribed values froze at their last GOOD quality and every write failed with `Session … was not found` until a process restart (QA incident, vq03 Z28061 MoveIn, one hour of silent loss; the 10-second `NotFound` heartbeat in the logs was the unresolved-tag resolution probe re-subscribing on the dead session). Same bug class as the gRPC site-stream client's graceful-completion reconnect. Pinned by `MxGatewayDataConnectionReconnectTests.EventStreamGracefulCompletion_*` (signals once while connected; silent for a superseded loop and after our own `DisconnectAsync`). Follow-up for the gateway SDK: `NotFound` maps to a generic `MxGatewayException` with only the detail text, so a write/subscribe hitting a dead session cannot be classified as a session loss without string matching — a typed session-not-found exception would allow a second, reactive detection layer.
 - Implemented as `MxGatewayDataConnection` over an `IMxGatewayClient` seam; the seam is decoupled from the generated gRPC types (only `RealMxGatewayClient` references them), so the adapter is fully unit-testable with a fake.
 
 ## Endpoint Redundancy