feat: add export_sch_bom tool (kicad-cli, schematic BOM)

New MCP tool `export_sch_bom` wrapping `kicad-cli sch export bom`: exposes
the full BOM option set (presets, field/label lists, group-by, sort
field/direction, filter, exclude-DNP, include-excluded-from-BOM, and the
field/string/ref/ref-range delimiters, plus keep-tabs/keep-line-breaks).
schematicPath is required and validated. Self-contained interface handler.

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

src/tools/registry.ts

@@ -70,6 +70,7 @@ export const toolCategories: ToolCategory[] = [
       "export_pcb_dxf",
       "export_gerber_single",
       "export_3d_cli",
+      "export_sch_bom",
       "export_pdf",
       "export_svg",
       "export_3d",