big rewrite of llm code; cost tracking now works, marker for number of completions in flight; fixed small bugs

Author: stephenfreund

src/flowco.py

@@ -14,7 +14,6 @@
 from flowco.util.costs import CostTracker
 from flowco.util.files import get_flowco_files, setup_flowco_files
 from flowco.util.output import Output, log, log_timestamp
-# from flowco.util.stopper import Stopper
 
 
 @st.cache_data