fix(comments): soften "bit-exact" to "~1e-15 floating-point rounding" in velocity_curve

src/vst/velocity_curve.h

@@ -63,8 +63,9 @@ inline constexpr int kCurveNodeGrabRadius = 6;
 // curved response (Daniel 2026-07-27: "straight lines sound like shit"), not a polyline. Each
 // velocity still maps to exactly one amp: the interpolant is single-valued and provably stays within
 // each segment's amp range, so the curve never overshoots below 0 or above 1. For COLLINEAR knots the
-// Fritsch–Carlson tangents reduce to the secant slope, so the spline IS the straight line — that
-// keeps linear() an EXACT y = velocity/127 (the Option-B / null-response contract). The two endpoints
+// Fritsch–Carlson tangents reduce to the secant slope, so the spline reproduces the straight line to
+// within floating-point rounding (~1e-15) — that preserves linear()'s null-response contract
+// (y = velocity/127 to ~1e-15; the 1e-12 test tolerance is deliberately conservative). The two endpoints
 // (velocity 0 and 127) are load-bearing: they keep eval total and are never deletable.
 class VelocityCurve {
 public:
@@ -90,7 +91,8 @@ public:
     // so an out-of-range note (shouldn't occur) reads the nearest endpoint. Between two adjacent
     // points the amp follows a MONOTONE cubic Hermite spline (Fritsch–Carlson slope limiting) — a
     // true curve that provably stays within the two knots' amp range (no overshoot below 0 / above
-    // 1) and reduces to the exact straight line for collinear knots. Single-valued / monotonic in X.
+    // 1) and reproduces the straight line to within floating-point rounding (~1e-15) for collinear
+    // knots. Single-valued / monotonic in X.
     // Degenerate cases (shouldn't occur post-construction): an EMPTY curve returns kAmpMax (flat
     // unity); a ONE-point curve returns that point's amp.
     double eval(double velocity) const;