DefaultJvmRecordingWarmupMillis

Default warmup window applied to JavaSound captures so the silent priming frames a TargetDataLine produces on the first read are dropped before we start emitting audio downstream.

Empirically, macbook-class hosts under JavaSound need ~150–250 ms before real audio starts arriving (see GitHub issue #5). 200 ms is conservative enough to swallow that gap on every host we've measured without noticeably trimming user audio.