Rebuffering ratio calculator

A dependency-free (pure standard-library) Python tool that turns a list of playback stall events into the streaming-QoE numbers the way the standards define them. It does NOT decode video or compute a picture metric; a rebuffering ratio comes from PLAYER EVENTS, not pixels. (1) REBUFFERING RATIO using the CTA-2066 denominator stall_time / (stall_time + play_time), with startup excluded; reproduces the article's 27 / (27 + 2700) = 0.99% worked example. (2) FREQUENCY in stalls per hour (catches th