refactor(demos): follow the Table-B1 rename and the marked resource names

The shipped machine tool is now MachineTool/Table-B1.default/Table-B1.mt
and the shipped cutting-parameter / workpiece-material files carry the
`.default` marker, so the three hard-coded resource paths move with them.
These samples are compiled into the public docsite verbatim, so a stale
path here ships as documentation.

Also removes the commented-out PmcB1MachineToolSource line and renames
the class summary, both of which put the retired name on the public docs.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

MachineTool/DemoBuildMachineTool.cs

@@ -15,7 +15,7 @@ using System.Xml.Linq;
 namespace Sample.MachineTool
 {
     /// <summary>
-    /// Provides access to the PMC-B1 machine tool model.
+    /// Provides access to the Table-B1 machine tool model.
     /// </summary>
     /// <remarks>
     /// ### Source Code
@@ -74,7 +74,6 @@ namespace Sample.MachineTool
             MachineTool = GenXyzabcMachineTool();
         }
         #region XML IO
-        //public PmcB1MachineToolSource(XElement src, object res) : this() { }
         /// <summary>
         /// XML element name for serialization.
         /// </summary>