Close Γ-W3-T2 review remediation: widen the bake-reset test's per-parameter coverage, correct four overclaiming comments, state the stage-time ceiling's disposition, and fix a missing include

Dials and asserts pitch-env/filter-env/trigEnv fields the sweep previously skipped in both fixtures; no reset behavior changed.

tests/test_bake_render.cpp

@@ -232,10 +232,12 @@ int main() {
     }
 
     // --- 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.
+    // A Trigger voice at its own root under Varispeed reads at ratio exactly 1 and hits no
+    // filter, so every printed frame equals its source frame PROVIDED the amp curve's gain at
+    // the plan's velocity is exactly 1.0 too (asserted below rather than assumed) — that exact
+    // value is a property of flat()'s two endpoints cancelling at velocity 100, not a
+    // guarantee of eval() at an arbitrary velocity. 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);
@@ -249,6 +251,7 @@ int main() {
 
         // Shorter than the play span, so the window closes before any note-end shaping.
         const BakePlan plan = planOf(/*total=*/1000, /*noteOn=*/0, /*noteOff=*/1000);
+        CHECK(s.velocityCurve.eval(100.0) == 1.0);  // names the real cause if this ever fails
         const BakeAudio audio = renderBake(s, plan, kUnity);
         CHECK(audio.channelCount == 1);
         CHECK(audio.frameCount() == 1000);