fix(abcip): accept module-defined I/O tag paths (Local:1:I.Data, ABB_OmniCore:I.X)

Live read-only check: a production CompactLogix lists the module tag ABB_OmniCore:I in
@tags and libplctag reads ABB_OmniCore:I.ConnectionFaulted without complaint, but the
driver refused the path as malformed (identifier rule had no colon) and reported the
tag BadCommunicationError. Colon-separated identifier/slot parts are now legal in the
controller-scope base segment only (never past it, never under Program: scope).

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.AbCip/AbCipTagPath.cs

@@ -100,7 +100,10 @@ public sealed record AbCipTagPath(
             var bracketIdx = part.IndexOf('[');
             if (bracketIdx < 0)
             {
-                if (!IsValidIdent(part)) return null;
+                // The controller-scope base name of a module-defined I/O tag carries colons
+                // (Local:1:I, ABB_OmniCore:I) — legal in the first segment only.
+                var isModuleBase = segments.Count == 0 && programScope is null && IsValidModuleBase(part);
+                if (!isModuleBase && !IsValidIdent(part)) return null;
                 segments.Add(new AbCipTagPathSegment(part, []));
                 continue;
             }
@@ -122,6 +125,25 @@ public sealed record AbCipTagPath(
         return new AbCipTagPath(programScope, segments, bitIndex);
     }
 
+    /// <summary>
+    ///     <c>true</c> for a module-defined I/O tag base name: an identifier followed by one or more
+    ///     <c>:</c>-separated identifier or slot-number parts (<c>Local:1:I</c>, <c>ABB_OmniCore:I</c>).
+    /// </summary>
+    /// <param name="s">The candidate base name.</param>
+    /// <returns><c>true</c> when <paramref name="s"/> is a module tag base name.</returns>
+    private static bool IsValidModuleBase(string s)
+    {
+        var parts = s.Split(':');
+        if (parts.Length < 2 || !IsValidIdent(parts[0])) return false;
+        for (var i = 1; i < parts.Length; i++)
+        {
+            var p = parts[i];
+            if (p.Length == 0) return false;
+            if (!IsValidIdent(p) && !p.All(char.IsAsciiDigit)) return false;
+        }
+        return true;
+    }
+
     private static bool IsValidIdent(string s)
     {
         if (string.IsNullOrEmpty(s)) return false;

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.AbCip.Tests/AbCipTagPathTests.cs

@@ -128,6 +128,41 @@ public sealed class AbCipTagPathTests
         AbCipTagPath.TryParse(input).ShouldBeNull();
     }
 
+    /// <summary>
+    ///     Module-defined I/O tags carry colons in their base name (<c>Local:1:I</c>,
+    ///     <c>ABB_OmniCore:I</c>). Seen live: a CompactLogix lists <c>ABB_OmniCore:I</c> in
+    ///     <c>@tags</c>, libplctag reads <c>ABB_OmniCore:I.ConnectionFaulted</c> fine, and the driver
+    ///     refused it as a malformed path.
+    /// </summary>
+    /// <param name="input">A module tag path.</param>
+    /// <param name="baseName">The expected base (first segment) name.</param>
+    [Theory]
+    [InlineData("ABB_OmniCore:I.ConnectionFaulted", "ABB_OmniCore:I")]
+    [InlineData("Local:1:I.Data", "Local:1:I")]
+    [InlineData("Local:2:O.Data.3", "Local:2:O")]
+    [InlineData("Rack1:3:C.Ch0Config.RangeType", "Rack1:3:C")]
+    public void Module_IO_tag_base_names_with_colons_parse_and_round_trip(string input, string baseName)
+    {
+        var parsed = AbCipTagPath.TryParse(input);
+        parsed.ShouldNotBeNull();
+        parsed.ProgramScope.ShouldBeNull();
+        parsed.Segments[0].Name.ShouldBe(baseName);
+        parsed.ToLibplctagName().ShouldBe(input);
+    }
+
+    /// <summary>A colon is only legal in the base name, and never as a dangling or doubled separator.</summary>
+    /// <param name="input">A malformed path.</param>
+    [Theory]
+    [InlineData("Motor.Sub:I")]          // colon past the base segment
+    [InlineData("Local::I.Data")]        // empty colon part
+    [InlineData("Local:1:.Data")]        // trailing colon
+    [InlineData(":Local.Data")]          // leading colon
+    [InlineData("Program:P.Local:1:I")]  // module tags are controller-scope only
+    public void Colons_outside_a_module_base_name_are_rejected(string input)
+    {
+        AbCipTagPath.TryParse(input).ShouldBeNull();
+    }
+
     /// <summary>Verifies that identifiers with underscores are accepted.</summary>
     [Fact]
     public void Ident_with_underscore_accepted()