Does the compiler generate intermediate assembler?
My source files are *.ino, but after compilation there aren't any other files placed in the folder.


Correct. The Arduino IDE performs compilation in a separate temporary directory, whose location you can see if you enable verbose compilation in the IDE options.


  Does the compiler generate intermediate assembler, and if so, where does it leave them?


By default GCC (which the Arduino IDE uses) does not leave intermediate assembly language files on disk. You must pass the --save-temps argument to have it leave them in the current directory, or --save-temps=obj to save them in the output directory.


  Or is the machine code available somewhere?


The machine code is available in the .elf and .hex files generated in the temprary directory.