ffmpeg filter args with commas? escape them or die trying

Commas are ffmpeg's filter-chain separator, so any comma INSIDE a filter arg (like drawtext text with "hello, world") silently breaks everything without a clear error. Two fixes: (1) escape inline with \, as in text=hello\,world, or (2) wrap the whole filter expression in single quotes. AI-generated ffmpeg commands fail here more than anywhere else. 3 hours of debug becomes 0.