deprecate(lmxproxy): move all LmxProxy code, tests, and docs to deprecated/

LmxProxy is no longer needed. Moved the entire lmxproxy/ workspace, DCL
adapter files, and related docs to deprecated/. Removed LmxProxy registration
from DataConnectionFactory, project reference from DCL, protocol option from
UI, and cleaned up all requirement docs.

deprecated/lmxproxy/docs/requirements/Component-MxAccessClient.md

@@ -0,0 +1,108 @@
+# Component: MxAccessClient
+
+## Purpose
+
+The core component that wraps the ArchestrA MXAccess COM API, providing connection management, tag read/write operations, and subscription-based value change notifications. This is the bridge between the gRPC service layer and AVEVA System Platform.
+
+## Location
+
+`src/ZB.MOM.WW.LmxProxy.Host/MxAccess/MxAccessClient.cs` — partial class split across 6 files:
+- `MxAccessClient.cs` — Main class, properties, disposal, factory.
+- `MxAccessClient.Connection.cs` — Connection lifecycle (connect, disconnect, reconnect, cleanup).
+- `MxAccessClient.ReadWrite.cs` — Read and write operations with retry and concurrency control.
+- `MxAccessClient.Subscription.cs` — Subscription management and stored subscription state.
+- `MxAccessClient.EventHandlers.cs` — COM event handlers (OnDataChange, OnWriteComplete, OperationComplete).
+- `MxAccessClient.NestedTypes.cs` — Internal types and enums.
+
+## Responsibilities
+
+- Manage the MXAccess COM object lifecycle (create, register, unregister, release).
+- Maintain connection state (Disconnected, Connecting, Connected, Disconnecting, Error, Reconnecting) and fire state change events.
+- Execute read and write operations against MXAccess with concurrency control via semaphores.
+- Manage tag subscriptions via MXAccess advise callbacks and store subscription state for reconnection.
+- Handle COM threading constraints (STA thread context via `Task.Run`).
+
+## 1. Connection Lifecycle
+
+### 1.1 Connect
+
+`ConnectAsync()` wraps `ConnectInternal()` in `Task.Run` for STA thread context:
+
+1. Validates not disposed.
+2. Returns early if already connected.
+3. Sets state to `Connecting`.
+4. `InitializeMxAccessConnection()` — creates new `LMXProxyServer` COM object, wires event handlers (OnDataChange, OnWriteComplete, OperationComplete).
+5. `RegisterWithMxAccess()` — calls `_lmxProxy.Register("ZB.MOM.WW.LmxProxy.Host")`, stores the returned connection handle.
+6. Sets state to `Connected`.
+7. On error, calls `Cleanup()` and re-throws.
+
+After successful connection, calls `RecreateStoredSubscriptionsAsync()` to restore any previously active subscriptions.
+
+### 1.2 Disconnect
+
+`DisconnectAsync()` wraps `DisconnectInternal()` in `Task.Run`:
+
+1. Checks `IsConnected`.
+2. Sets state to `Disconnecting`.
+3. `RemoveAllSubscriptions()` — unsubscribes all tags from MXAccess but retains subscription state in `_storedSubscriptions` for reconnection.
+4. `UnregisterFromMxAccess()` — calls `_lmxProxy.Unregister(_connectionHandle)`.
+5. `Cleanup()` — removes event handlers, calls `Marshal.ReleaseComObject(_lmxProxy)` to force-release all COM references, nulls the proxy and resets the connection handle.
+6. Sets state to `Disconnected`.
+
+### 1.3 Connection State
+
+- `IsConnected` property: `_lmxProxy != null && _connectionState == Connected && _connectionHandle > 0`.
+- `ConnectionState` enum: Disconnected, Connecting, Connected, Disconnecting, Error, Reconnecting.
+- `ConnectionStateChanged` event fires on all state transitions with previous state, current state, and optional message.
+
+### 1.4 Auto-Reconnect
+
+When `AutoReconnect` is enabled (default), the `MonitorConnectionAsync` loop runs continuously:
+- Checks `IsConnected` every `MonitorIntervalSeconds` (default 5 seconds).
+- On disconnect, attempts reconnect via semaphore-protected `ConnectAsync()`.
+- On failure, logs warning and retries at the next interval.
+- Reconnection restores stored subscriptions automatically.
+
+## 2. Thread Safety & COM Constraints
+
+- State mutations protected by `lock (_lock)`.
+- COM operations wrapped in `Task.Run` for STA thread context (MXAccess is 32-bit COM).
+- Concurrency control: `_readSemaphore` and `_writeSemaphore` limit concurrent MXAccess operations to `MaxConcurrentOperations` (default 10, configurable).
+- Default max concurrency constant: `DefaultMaxConcurrency = 10`.
+
+## 3. Read Operations
+
+- `ReadAsync(address, ct)` — Applies Polly retry policy, calls `ReadSingleValueAsync()`, returns `Vtq`.
+- `ReadBatchAsync(addresses, ct)` — Creates parallel tasks per address via `ReadAddressWithSemaphoreAsync()`. Each task acquires `_readSemaphore` before reading. Returns `IReadOnlyDictionary<address, Vtq>`.
+
+## 4. Write Operations
+
+- `WriteAsync(address, value, ct)` — Applies Polly retry policy, calls `WriteInternalAsync(address, value, ct)`.
+- `WriteBatchAsync(values, ct)` — Parallel tasks via `WriteAddressWithSemaphoreAsync()`. Each task acquires `_writeSemaphore` before writing.
+- `WriteBatchAndWaitAsync(values, flagAddress, flagValue, responseAddress, responseValue, ct)` — Writes batch, writes flag, polls response tag until match.
+
+## 5. Subscription Management
+
+- Subscriptions stored in `_storedSubscriptions` for reconnection persistence.
+- `SubscribeInternalAsync(addresses, callback, storeSubscription)` — registers tags with MXAccess and stores subscription state.
+- `RecreateStoredSubscriptionsAsync()` — called after reconnect to re-subscribe all previously active tags without re-storing.
+- `RemoveAllSubscriptions()` — unsubscribes from MXAccess but retains `_storedSubscriptions`.
+
+## 6. Event Handlers
+
+- **OnDataChange** — Fired by MXAccess when a subscribed tag value changes. Routes the update to the SubscriptionManager.
+- **OnWriteComplete** — Fired when an async write operation completes.
+- **OperationComplete** — General operation completion callback.
+
+## Dependencies
+
+- **ArchestrA.MXAccess** COM interop assembly (`lib/ArchestrA.MXAccess.dll`).
+- **Polly** — retry policies for read/write operations.
+- **Configuration** — `ConnectionConfiguration` for timeouts, concurrency limits, and auto-reconnect settings.
+
+## Interactions
+
+- **GrpcServer** (ScadaGrpcService) delegates all SCADA operations to MxAccessClient via the `IScadaClient` interface.
+- **SubscriptionManager** receives value change callbacks originating from MxAccessClient's COM event handlers.
+- **HealthAndMetrics** queries `IsConnected` and `ConnectionState` for health checks.
+- **ServiceHost** manages the MxAccessClient lifecycle (create at startup, dispose at shutdown).