The CPU-thread polling added for SDL was keyed off defined(SDL), which
headless and Core are built with too, hence the extra headless check.
Ask the host instead, with SYSPROP_MICROPHONE_NEEDS_POLLING, so other
hosts can hand their input over the same way.
startMic now sends the same startRecording command for every non-Win32
host, taking the rate from curSampleRate like the SDL path did. The
Android path read it from param, which leaked, and which is null when
coming from onMicDeviceChange.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
