docs(src): add missing XML docs and strip tracking-ID comments

Sweep of 203 source files resolving CommentChecker findings: add
<summary>/<param>/<returns>/<inheritdoc> where missing, and remove
resolved task/issue tracking markers (Tests-NNN, Worker-NNN, Server-NNN,
Task N) from code comments. Comment/doc-only — no logic changes.
Server+Tests build clean under TreatWarningsAsErrors.

src/ZB.MOM.WW.MxGateway.Tests/Gateway/Sessions/SparseArrayExpanderTests.cs

@@ -26,6 +26,7 @@ public sealed class SparseArrayExpanderTests
         return new MxValue { SparseArrayValue = sparse };
     }
 
+    /// <summary>Verifies that expanding an Int32 sparse array fills unset indices with the default and applies the given element.</summary>
     [Fact]
     public void Expand_Int32_FillsDefaultsAndSetsElement()
     {
@@ -43,6 +44,7 @@ public sealed class SparseArrayExpanderTests
         Assert.Equal(new[] { 0, 7, 0, 0 }, value.ArrayValue.Int32Values.Values);
     }
 
+    /// <summary>Verifies that expanding a Boolean sparse array with no elements fills every index with the default value <c>false</c>.</summary>
     [Fact]
     public void Expand_Boolean_EmptyElements_AllDefaultFalse()
     {
@@ -54,6 +56,7 @@ public sealed class SparseArrayExpanderTests
         Assert.Equal(new[] { false, false, false }, value.ArrayValue.BoolValues.Values);
     }
 
+    /// <summary>Verifies that expanding a sparse array with a zero total length throws an invalid-argument <see cref="RpcException"/>.</summary>
     [Fact]
     public void Expand_ZeroTotalLength_Throws()
     {
@@ -63,6 +66,7 @@ public sealed class SparseArrayExpanderTests
         Assert.Equal(StatusCode.InvalidArgument, ex.StatusCode);
     }
 
+    /// <summary>Verifies that an element index at or beyond the total length throws an invalid-argument <see cref="RpcException"/>.</summary>
     [Fact]
     public void Expand_IndexOutOfRange_Throws()
     {
@@ -75,6 +79,7 @@ public sealed class SparseArrayExpanderTests
         Assert.Equal(StatusCode.InvalidArgument, ex.StatusCode);
     }
 
+    /// <summary>Verifies that two sparse elements sharing the same index throw an invalid-argument <see cref="RpcException"/>.</summary>
     [Fact]
     public void Expand_DuplicateIndex_Throws()
     {
@@ -88,6 +93,7 @@ public sealed class SparseArrayExpanderTests
         Assert.Equal(StatusCode.InvalidArgument, ex.StatusCode);
     }
 
+    /// <summary>Verifies that an unspecified element data type throws an invalid-argument <see cref="RpcException"/>.</summary>
     [Fact]
     public void Expand_UnsupportedElementType_Throws()
     {
@@ -97,6 +103,7 @@ public sealed class SparseArrayExpanderTests
         Assert.Equal(StatusCode.InvalidArgument, ex.StatusCode);
     }
 
+    /// <summary>Verifies that an element value whose kind does not match the declared element data type throws an invalid-argument <see cref="RpcException"/>.</summary>
     [Fact]
     public void Expand_ElementValueKindMismatch_Throws()
     {
@@ -109,6 +116,7 @@ public sealed class SparseArrayExpanderTests
         Assert.Equal(StatusCode.InvalidArgument, ex.StatusCode);
     }
 
+    /// <summary>Verifies that expanding a String sparse array fills unset indices with an empty string default.</summary>
     [Fact]
     public void Expand_String_FillsEmptyStringDefault()
     {
@@ -123,6 +131,7 @@ public sealed class SparseArrayExpanderTests
         Assert.Equal(new[] { "a", string.Empty }, value.ArrayValue.StringValues.Values);
     }
 
+    /// <summary>Verifies that expanding a Time sparse array fills unset indices with the epoch timestamp default.</summary>
     [Fact]
     public void Expand_Time_FillsEpochDefault()
     {
@@ -140,6 +149,7 @@ public sealed class SparseArrayExpanderTests
         Assert.Equal(5, value.ArrayValue.TimestampValues.Values[1].Seconds);
     }
 
+    /// <summary>Verifies that expanding a Double sparse array fills defaults and applies the given element.</summary>
     [Fact]
     public void Expand_Double_HappyPath()
     {
@@ -154,6 +164,7 @@ public sealed class SparseArrayExpanderTests
         Assert.Equal(new[] { 0d, 0d, 1.5 }, value.ArrayValue.DoubleValues.Values);
     }
 
+    /// <summary>Verifies that expanding a Float sparse array fills defaults and applies the given element.</summary>
     [Fact]
     public void Expand_Float_HappyPath()
     {
@@ -168,6 +179,7 @@ public sealed class SparseArrayExpanderTests
         Assert.Equal(new[] { 2.5f, 0f }, value.ArrayValue.FloatValues.Values);
     }
 
+    /// <summary>Verifies that an Integer sparse array whose element is a 64-bit value expands to the Int64 array representation.</summary>
     [Fact]
     public void Expand_Int64_WhenElementIsInt64()
     {
@@ -182,6 +194,7 @@ public sealed class SparseArrayExpanderTests
         Assert.Equal(new[] { 0L, 0L, 9_000_000_000L }, value.ArrayValue.Int64Values.Values);
     }
 
+    /// <summary>Verifies that expanding a non-sparse-array value is a no-op, leaving the original value unchanged.</summary>
     [Fact]
     public void Expand_NonSparseValue_NoOps()
     {
@@ -193,12 +206,14 @@ public sealed class SparseArrayExpanderTests
         Assert.Equal(42, value.Int32Value);
     }
 
+    /// <summary>Verifies that expanding a null value throws <see cref="ArgumentNullException"/>.</summary>
     [Fact]
     public void Expand_NullValue_ThrowsArgumentNull()
     {
         Assert.Throws<ArgumentNullException>(() => SparseArrayExpander.Expand(null!));
     }
 
+    /// <summary>Verifies that a total length exceeding the maximum supported array length throws an invalid-argument <see cref="RpcException"/>.</summary>
     [Fact]
     public void Expand_TotalLengthExceedsMaxArrayLength_Throws()
     {