Play cross-rate captures at their own pitch and length

The voice now converts the file's rate to the host's at note-on instead of assuming they match. Stage times resolve at the host rate, the filter solves at it, and the bake follows. Same-rate renders are unchanged bit for bit.

tests/test_period_render_integration.cpp

@@ -79,7 +79,7 @@ static void testDetectedPeriodReachesAndMovesThePreserveRender() {
     ref.relativePath = "b/a.wav";
     ref.rootNote = 60;
     SampleData on = buildSampleData(resolveCapture(ref, InstrumentParams{}),
-                                    DecodedPcm{pcm, rate, {}});
+                                    DecodedPcm{pcm, rate, {}}, rate);
     CHECK(std::fabs(on.sourcePeriodFrames - 1470.0) < 2.0);  // 44100 / 30 Hz, real detection
 
     on.play.adsr = flatAdsr();