#kuro updates

• node lifetime supervision with auto destruction of associated 9pfs is working
• buffered reads of large files are implemented
• framework for executing arbitrary text is implemented

the main pieces of the backend that still need implementing are the auto generation of the text in TAG and EXE panes, the plumbing client, and Look (find) and Edit (sam style regex) opcodes. regardless i think now is a good time to write the unit tests around the core functionality