Bake reset: assert the limiter and bake Hold land neutral, prove the loop returns parked, and baseline the render's identity path

resetAfterBake is unchanged — every value already resets by construction. The render prints master gain but not the limiter, so §3.4's rationale is wrong; the invariant is corrected.

tests/test_bake_render.cpp

@@ -231,6 +231,42 @@ int main() {
         CHECK(identical);
     }
 
+    // --- Regression baseline: the neutral render is the source, sample for sample --------
+    // DERIVED rather than recorded, so it survives a compiler change: a Trigger voice at its
+    // own root under Varispeed, with the default flat amp and velocity shapes and no filter,
+    // reads at ratio exactly 1 — so every printed frame must BE its source frame. An added
+    // stage, a moved default, or a lost early-out anywhere in the chain moves a sample here.
+    {
+        SampleData s;
+        s.frames.resize(4000);
+        // A ramp, not DC: an off-by-one read or a reversed span is invisible in a constant.
+        for (std::size_t i = 0; i < s.frames.size(); ++i)
+            s.frames[i] = static_cast<float>(i) / 4000.f - 0.5f;
+        s.sampleRate = kRate;
+        s.rootNote = 60;
+        s.play.playMode = PlayMode::Trigger;
+        s.play.pitchEngine = PitchEngine::Varispeed;
+
+        // Shorter than the play span, so the window closes before any note-end shaping.
+        const BakePlan plan = planOf(/*total=*/1000, /*noteOn=*/0, /*noteOff=*/1000);
+        const BakeAudio audio = renderBake(s, plan, kUnity);
+        CHECK(audio.channelCount == 1);
+        CHECK(audio.frameCount() == 1000);
+
+        bool identity = audio.frameCount() == 1000;
+        for (std::size_t f = 0; identity && f < 1000; ++f)
+            identity = (audio.interleaved[f] == s.frames[f]);
+        CHECK(identity);
+
+        // …and the gain rides that as an exact scalar, which is the only other thing the
+        // render is permitted to do to the signal.
+        const BakeAudio halved = renderBake(s, plan, 0.5);
+        bool scaled = halved.frameCount() == 1000;
+        for (std::size_t f = 0; scaled && f < 1000; ++f)
+            scaled = (halved.interleaved[f] == s.frames[f] * 0.5f);
+        CHECK(scaled);
+    }
+
     // --- Refusals -----------------------------------------------------------------------
     {
         SampleData empty;  // nothing decoded