fix: prevent header corruption when sexpdata compacts schematic to single line

create_component_instance used line-based insertion which placed new
symbols BEFORE (kicad_sch ...) header when the file was written as
a single line by sexpdata.dumps(). Switch to rfind()-based string
insertion which is format-independent.

Also remove StreamHandler(sys.stdout) from logging — Python logs now
go only to file (~/.kicad-mcp/logs/kicad_interface.log) to avoid
polluting MCP stderr with INFO/DEBUG entries shown as [error].

python/kicad_interface.py

@@ -26,7 +26,7 @@ log_file = os.path.join(log_dir, "kicad_interface.log")
 logging.basicConfig(
     level=logging.DEBUG,
     format="%(asctime)s [%(levelname)s] %(message)s",
-    handlers=[logging.FileHandler(log_file), logging.StreamHandler(sys.stdout)],
+    handlers=[logging.FileHandler(log_file)],
 )
 logger = logging.getLogger("kicad_interface")