fix(mtconnect): options carry the authored tag definitions (Task 2 follow-up)

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.MTConnect.Contracts/MTConnectDriverOptions.cs

@@ -54,6 +54,21 @@ public sealed class MTConnectDriverOptions
     /// </summary>
     public int HeartbeatMs { get; init; } = 10000;
 
+    /// <summary>
+    ///     The authored tags this driver instance serves — one <see cref="MTConnectTagDefinition"/>
+    ///     per tag, keyed by the DataItem <c>id</c> it binds
+    ///     (<see cref="MTConnectTagDefinition.FullName"/>). The factory config DTO carries these and
+    ///     builds them into the options; the driver indexes them to know each tag's target
+    ///     <see cref="MTConnectTagDefinition.DriverDataType"/> when coercing an Agent observation
+    ///     (whose wire form is always text) into a published value.
+    ///     <para>
+    ///         Defaults to <b>empty, never <c>null</c></b>: a driver instance may legitimately be
+    ///         authored with no tags yet, and a null collection here would surface as a
+    ///         NullReferenceException at deploy time from operator-authored config.
+    ///     </para>
+    /// </summary>
+    public IReadOnlyList<MTConnectTagDefinition> Tags { get; init; } = [];
+
     /// <summary>
     ///     Background connectivity-probe settings. When <see cref="MTConnectProbeOptions.Enabled"/>
     ///     is true the driver periodically issues a cheap <c>/probe</c> request and raises

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.MTConnect.Tests/MTConnectDriverOptionsTests.cs

@@ -56,6 +56,47 @@ public sealed class MTConnectDriverOptionsTests
         reconnect.BackoffMultiplier.ShouldBeGreaterThan(1.0);
     }
 
+    /// <summary>
+    ///     <see cref="MTConnectDriverOptions.Tags"/> defaults to an <i>empty</i> collection, never
+    ///     <c>null</c> — a null collection here is an operator-authorable NullReferenceException at
+    ///     deploy, since a driver instance authored with no tags binds this default.
+    /// </summary>
+    [Fact]
+    public void Options_tags_default_to_empty_and_are_never_null()
+    {
+        var o = new MTConnectDriverOptions { AgentUri = "http://agent:5000" };
+
+        o.Tags.ShouldNotBeNull();
+        o.Tags.ShouldBeEmpty();
+    }
+
+    /// <summary>
+    ///     A populated options object carries the authored tag definitions through unchanged —
+    ///     the observation index (Task 8) coerces each present observation to <i>its tag's</i>
+    ///     DriverDataType, so the definitions must reach the driver from the factory config.
+    /// </summary>
+    [Fact]
+    public void Options_round_trip_the_authored_tag_definitions()
+    {
+        var pos = new MTConnectTagDefinition(
+            FullName: "dev1_pos",
+            DriverDataType: ZB.MOM.WW.OtOpcUa.Core.Abstractions.DriverDataType.Float64,
+            MtCategory: "SAMPLE",
+            MtType: "POSITION",
+            Units: "MILLIMETER");
+        var partCount = new MTConnectTagDefinition(
+            FullName: "dev1_partcount",
+            DriverDataType: ZB.MOM.WW.OtOpcUa.Core.Abstractions.DriverDataType.Int64,
+            MtCategory: "EVENT",
+            MtType: "PART_COUNT");
+
+        var o = new MTConnectDriverOptions { AgentUri = "http://agent:5000", Tags = [pos, partCount] };
+
+        o.Tags.Count.ShouldBe(2);
+        o.Tags[0].ShouldBe(pos);
+        o.Tags[1].ShouldBe(partCount);
+    }
+
     /// <summary>MTConnectTagDefinition round-trips its positional fields, including MTConnect metadata.</summary>
     [Fact]
     public void TagDefinition_carries_dataItemId_and_mtconnect_metadata()