Auto: s7-c3 — per-tag scan group / publish rate

Closes #296

src/ZB.MOM.WW.OtOpcUa.Driver.S7/S7DriverOptions.cs

@@ -122,6 +122,23 @@ public sealed class S7DriverOptions
     ///     non-<see cref="TsapMode.Auto"/> mode.
     /// </summary>
     public ushort? RemoteTsap { get; init; }
+
+    /// <summary>
+    ///     PR-S7-C3 — per-tag scan-group → publishing-interval map. When a tag declares a
+    ///     <see cref="S7TagDefinition.ScanGroup"/>, <see cref="S7Driver.SubscribeAsync"/>
+    ///     resolves its publishing rate by looking the group up in this dictionary; tags
+    ///     without a group, or with a group not present here, fall back to the
+    ///     subscription-default <c>publishingInterval</c> argument. Keys are matched
+    ///     case-insensitively. See <c>docs/v2/s7.md</c> "Per-tag scan groups" section.
+    /// </summary>
+    /// <remarks>
+    ///     The driver still owns one <c>Plc</c> connection serialized through the per-driver
+    ///     <c>_gate</c>, so partitioning into N poll loops does NOT parallelise wire-level
+    ///     reads — every partition queues against the same semaphore. Operator value is
+    ///     decoupling tick cadence: a 100 ms HMI tag isn't blocked behind a 10 s slow-poll
+    ///     batch any more, because the slow batch's <c>Task.Delay</c> isn't holding the gate.
+    /// </remarks>
+    public IReadOnlyDictionary<string, TimeSpan>? ScanGroupIntervals { get; init; }
 }
 
 /// <summary>
@@ -227,6 +244,15 @@ public sealed class S7ProbeOptions
 ///     they need bespoke layout handling and are tracked as a follow-up. Capped at 8000 to
 ///     keep the byte-range request inside a single S7 PDU envelope.
 /// </param>
+/// <param name="ScanGroup">
+///     PR-S7-C3 — optional scan-group identifier. When set, <c>SubscribeAsync</c> looks up
+///     the group's publishing interval in <see cref="S7DriverOptions.ScanGroupIntervals"/>
+///     and partitions the input tag list so all tags sharing that interval poll together
+///     in a dedicated background loop. Tags with no <c>ScanGroup</c>, or with a group not
+///     present in the map, fall back to the subscription's default publishing interval
+///     (legacy single-rate behaviour). Group names are matched case-insensitively. See
+///     <c>docs/v2/s7.md</c> "Per-tag scan groups" section.
+/// </param>
 public sealed record S7TagDefinition(
     string Name,
     string Address,
@@ -234,7 +260,8 @@ public sealed record S7TagDefinition(
     bool Writable = true,
     int StringLength = 254,
     bool WriteIdempotent = false,
-    int? ElementCount = null);
+    int? ElementCount = null,
+    string? ScanGroup = null);
 
 public enum S7DataType
 {