fix: macOS wxApp warm-up + symbol cache eager loading (#195)

Three-phase MCP server startup: wait for Python READY handshake, send
_warmup command (pcbnew.BOARD() triggers wxApp init on macOS), connect
to MCP transport only after warm-up completes.

Also pre-populate symbol library cache during SymbolLibraryManager
init so the first search_symbols call doesn't parse 241 .kicad_sym
files from disk (30-120s). Both warm-up and cache population happen
before tools are registered with the MCP client.

Fixes #195

python/commands/library_symbol.py

@@ -55,6 +55,21 @@ class SymbolLibraryManager:
         self.libraries: Dict[str, str] = {}  # nickname -> path mapping
         self.symbol_cache: Dict[str, List[SymbolInfo]] = {}  # library -> [SymbolInfo]
         self._load_libraries()
+        self._warm_cache()
+
+    def _warm_cache(self) -> None:
+        """Pre-parse all symbol libraries so the first search is fast.
+
+        Without this, the first ``search_symbols`` call parses every
+        .kicad_sym file on demand, which can take 30-120 s across
+        200+ libraries.  By populating the cache here (during startup,
+        before the READY handshake) the cost is paid once.
+        """
+        for nickname in list(self.libraries.keys()):
+            try:
+                self.list_symbols(nickname)
+            except Exception:
+                logger.debug("Skipping unparseable library: %s", nickname)
 
     def _load_libraries(self) -> None:
         """Load libraries from sym-lib-table files"""