Discover past Elodin runs (timestamped daq_[sim_]YYYYMMDD_HHMMSS dirs only).
List timestamped runs, newest first. Intentionally cheap: no per-run `du` (that would stat thousands of DB subdirs across every run). Size/duration are filled in by the per-run index once a run is opened.
Definition at line 10 of file runs.py.