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].