feat: add export_sch_python_bom tool (kicad-cli, legacy Python-BOM XML)

New MCP tool `export_sch_python_bom` wrapping `kicad-cli sch export
python-bom`: emits the legacy intermediate XML netlist consumed by the
schematic editor's Python BOM scripts. Minimal option set (outputPath +
schematicPath only, matching the subcommand's --help). schematicPath
required and validated.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/tools/registry.ts

@@ -76,6 +76,7 @@ export const toolCategories: ToolCategory[] = [
       "export_sch_dxf",
       "export_sch_hpgl",
       "export_sch_ps",
+      "export_sch_python_bom",
       "export_pdf",
       "export_svg",
       "export_3d",