feat: Add local symbol library search and 3rd party library support (#25)

Adds comprehensive local KiCad symbol library search functionality and fixes KICAD9_3RD_PARTY environment variable resolution.

Features:
- Symbol library search by name, LCSC ID, description, manufacturer, MPN
- Support for 3rd party libraries installed via Plugin and Content Manager
- New MCP tools: search_symbols, list_symbol_libraries, get_symbol_info
- Enhanced library path resolution for KiCad 8 and 9

This enables users with locally installed JLCPCB libraries to search and use components directly.

Co-authored-by: l3wi <l3wi@users.noreply.github.com>

src/server.ts

@@ -19,6 +19,7 @@ import { registerDesignRuleTools } from './tools/design-rules.js';
 import { registerExportTools } from './tools/export.js';
 import { registerSchematicTools } from './tools/schematic.js';
 import { registerLibraryTools } from './tools/library.js';
+import { registerSymbolLibraryTools } from './tools/library-symbol.js';
 import { registerUITools } from './tools/ui.js';
 import { registerRouterTools } from './tools/router.js';
 
@@ -153,6 +154,7 @@ export class KiCADMcpServer {
     registerExportTools(this.server, this.callKicadScript.bind(this));
     registerSchematicTools(this.server, this.callKicadScript.bind(this));
     registerLibraryTools(this.server, this.callKicadScript.bind(this));
+    registerSymbolLibraryTools(this.server, this.callKicadScript.bind(this));
     registerUITools(this.server, this.callKicadScript.bind(this));
 
     // Register all resources