Bake window: derived note lengths carry exact durations, not ladder rungs — a long take is no longer cut at 384 beats

Hold keeps its picker. Also: one home for the %-fold, duration-ordered Hold travel, and a corrupt tail degrades to absent rather than fabricating one.

tests/test_musical_division.cpp

@@ -9,7 +9,9 @@
 
 #include "../src/core/instrument/note/musical_division.h"
 
+#include <cmath>
 #include <cstdio>
+#include <limits>
 
 using namespace reasampler::instrument::note;
 
@@ -240,6 +242,11 @@ static void testShortestAtLeastDegenerateInputs() {
     const Division longest = makeDivision(kMaxQuarterExponent, DivisionModifier::Dotted);
     CHECK(almostEqual(divisionBeats(longest), kMaxDivisionBeats));
     CHECK(shortestDivisionAtLeast(kMaxDivisionBeats * 2.0) == longest);
+    // A non-finite request names no length to be at least, so it takes the SAME never-short
+    // answer as one nothing covers. Landing on the bottom rung instead would turn a corrupt
+    // value into a near-instant note.
+    CHECK(shortestDivisionAtLeast(std::nan("")) == longest);
+    CHECK(shortestDivisionAtLeast(std::numeric_limits<double>::infinity()) == longest);
 }
 
 int main() {