Auto: focas-f4d — password / unlock parameter

Closes #271

src/ZB.MOM.WW.OtOpcUa.Driver.FOCAS/IFocasClient.cs

@@ -23,6 +23,25 @@ public interface IFocasClient : IDisposable
     /// <summary>True when the FWLIB handle is valid + the socket is up.</summary>
     bool IsConnected { get; }
 
+    /// <summary>
+    ///     Plan PR F4-d (issue #271) — emit the CNC password via FOCAS
+    ///     <c>cnc_wrunlockparam</c>. Some controllers (notably 16i + some 30i
+    ///     firmwares with parameter-protect on) gate <c>cnc_wrparam</c> and selected
+    ///     reads behind a connection-level password; this call lifts the gate for
+    ///     the lifetime of the FWLIB handle (resets on reconnect, hence the driver
+    ///     re-issues unlock on every <see cref="ConnectAsync"/>).
+    ///     <para>Default impl is a no-op (<see cref="Task.CompletedTask"/>) so transport
+    ///     variants that don't surface unlock (today: IPC and FAKE clients) keep
+    ///     compiling. The FWLIB-backed client overrides this with a real
+    ///     <c>cnc_wrunlockparam</c> call.</para>
+    ///     <para><b>No-log invariant:</b> <paramref name="password"/> is a secret. The
+    ///     wire-client implementation MUST NOT log the password — see
+    ///     <c>FocasDeviceOptions.Password</c> + <c>docs/v2/focas-deployment.md</c>
+    ///     § "FOCAS password handling".</para>
+    /// </summary>
+    Task UnlockAsync(string password, CancellationToken cancellationToken)
+        => Task.CompletedTask;
+
     /// <summary>
     ///     Read the value at <paramref name="address"/> in the requested
     ///     <paramref name="type"/>. Returns a boxed .NET value + the OPC UA status mapped