Pure functions extracted from ui/recording-panel.ts so the
arithmetic + string-formatting paths are unit-testable without a
real MediaRecorder or DOM. The browser-coupled
getSupportedMimeType accepts an explicit MediaRecorder-like
argument so it can also be tested with a stub.
Media-utility helpers for the recording panel.
Pure functions extracted from
ui/recording-panel.tsso the arithmetic + string-formatting paths are unit-testable without a realMediaRecorderor DOM. The browser-coupled getSupportedMimeType accepts an explicit MediaRecorder-like argument so it can also be tested with a stub.