Apply the warm-review polish: parseInt radix 10, fall back to 1800 for
missing/NaN/non-positive values, and floor at 200ms so a mistyped tiny/negative
hermes-voice-silence-ms can't make the recognizer auto-send instantly. De-brittle
the source-string test to assert behavior (reads key / 1800 fallback / guards
non-positive) instead of one literal expression. Default behavior unchanged.