feat: add add_schematic_text and list_schematic_texts tools

Adds two new MCP tools for working with free-form text annotations
(SCH_TEXT elements) in KiCad schematics:

- add_schematic_text: place a text note with optional angle, font size,
  bold/italic, and justification
- list_schematic_texts: list all text annotations with optional
  case-insensitive substring filter

Includes WireManager.add_text / list_texts using _text_insert + sexpdata,
handler dispatch in KiCADInterface, TypeScript tool definitions, registry
entry, reference doc updates, and 30 unit tests.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/tools/registry.ts

@@ -109,6 +109,8 @@ export const toolCategories: ToolCategory[] = [
       "get_schematic_view",
       "export_schematic_svg",
       "export_schematic_pdf",
+      "add_schematic_text",
+      "list_schematic_texts",
     ],
   },
   {