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>

docs/TOOL_INVENTORY.md

@@ -169,6 +169,13 @@ _Source: `src/tools/schematic.ts`_
 | `list_schematic_wires`  | List all wires in schematic   | Routed (schematic) |
 | `list_schematic_labels` | List all net labels           | Routed (schematic) |
 
+### Text Annotations
+
+| Tool                   | Description                                      | Access             |
+| ---------------------- | ------------------------------------------------ | ------------------ |
+| `add_schematic_text`   | Add free-form text annotation to schematic       | Routed (schematic) |
+| `list_schematic_texts` | List all text annotations (with optional filter) | Routed (schematic) |
+
 ### Schematic Creation and Export
 
 | Tool                   | Description                      | Access             |