fix(focas): serialize per-device wire I/O + bound reads; tolerate AdminUI config formats

Equipment tags were stuck at Bad_WaitingForInitialData on the deployed driver: the equipment poll, fixed-tree loop, probe and recycle shared one FOCAS/2 socket with no serialization, and the steady-state read had no timeout — concurrent reads collided and a stalled read hung forever, never overwriting the node's initial-data seed.

- SynchronizedFocasClient: per-device SemaphoreSlim gate + per-call timeout around every wire op (Connect/Probe gated, not double-bounded); wired in EnsureConnectedAsync. ReadAsync/WriteAsync map a per-call timeout to BadCommunicationError instead of rethrowing.
- FlexibleStringConverter on FOCAS config Series: the AdminUI persists the enum as a number ("series":6); accept number-or-string instead of throwing -> stub.
- FocasHostAddress.TryParse tolerates a scheme-less {ip}[:{port}] (AdminUI hostAddress form); canonical focas:// unchanged, malformed schemes still rejected.

247 FOCAS tests green; each fix has a regression test. Live-validated on wonder-app-vd03 (tags read Good).

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.FOCAS.Tests/FocasReadWriteTests.cs

@@ -245,6 +245,32 @@ public sealed class FocasReadWriteTests
     /// <summary>Verifies that cancellation signals are propagated.</summary>
     [Fact]
     public async Task Cancellation_propagates()
+    {
+        var (drv, factory) = NewDriver(
+            new FocasTagDefinition("X", "focas://10.0.0.5:8193", "R100", FocasDataType.Byte));
+        await drv.InitializeAsync("{}", CancellationToken.None);
+        using var cts = new CancellationTokenSource();
+        cts.Cancel();
+        factory.Customise = () => new FakeFocasClient
+        {
+            ThrowOnRead = true,
+            Exception = new OperationCanceledException(cts.Token),
+        };
+
+        // A CANCELLATION of the caller's token must propagate (abort the read). This is distinct
+        // from a per-call timeout — an OCE raised while the caller's token is still live is swallowed
+        // to a per-tag BadCommunicationError (see Swallows_a_spurious_read_OCE_when_caller_not_cancelled).
+        await Should.ThrowAsync<OperationCanceledException>(
+            () => drv.ReadAsync(["X"], cts.Token));
+    }
+
+    /// <summary>
+    ///     An OperationCanceledException from the wire read while the CALLER'S token is NOT cancelled
+    ///     (e.g. a per-call timeout firing) must be turned into a per-tag BadCommunicationError, not
+    ///     propagated — otherwise one stalled tag would abort the whole poll batch.
+    /// </summary>
+    [Fact]
+    public async Task Swallows_a_spurious_read_OCE_when_caller_not_cancelled()
     {
         var (drv, factory) = NewDriver(
             new FocasTagDefinition("X", "focas://10.0.0.5:8193", "R100", FocasDataType.Byte));
@@ -255,8 +281,8 @@ public sealed class FocasReadWriteTests
             Exception = new OperationCanceledException(),
         };
 
-        await Should.ThrowAsync<OperationCanceledException>(
-            () => drv.ReadAsync(["X"], CancellationToken.None));
+        var snap = (await drv.ReadAsync(["X"], CancellationToken.None)).Single();
+        snap.StatusCode.ShouldBe(FocasStatusMapper.BadCommunicationError);
     }
 
     /// <summary>Verifies that ShutdownAsync disposes the client.</summary>