Follows the CodeXyzabcMachineTool retirement in HiMech. DemoBuildMachineTool
drops IGetCodeXyzabcMachineTool, which no longer exists, and spells out the
doc comments the inherited interface used to supply.
The two GenByFile<CodeXyzabcMachineTool> call sites are fixed rather than
merely renamed: they read Resource machine tools rooted at
<GeneralXyzabcMachineTool>, so the factory's `as` cast handed back null and
the demo project got no machining chain at all.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>