note: close out the model — correct an inert mutation claim, retag four non-discriminating assertions, assert Tempo's closure, fix three doc/test accuracy gaps

No behavior change; verification-record corrections and one static_assert.

tests/test_musical_division.cpp

@@ -175,6 +175,9 @@ static void testUnnamedModifierClampsToStraight() {
           == divisionIndex(makeDivision(0, DivisionModifier::Straight)));
     CHECK(divisionLabel(makeDivision(0, junk)) == "1/4");  // and no junk reaches the readout
     CHECK(makeDivision(0, junk) == makeDivision(0, DivisionModifier::Straight));
+    // Measured (clamp removed from clampModifier): still passes. junk(7) != Dotted's stored
+    // modifier either way, clamped or raw — this discriminates a degenerate operator== that
+    // ignores the modifier field, not the clamp itself.
     CHECK(makeDivision(0, junk) != makeDivision(0, DivisionModifier::Dotted));
 }
 
@@ -184,6 +187,8 @@ static void testEveryConstructibleDivisionIndexesIntoThePickerSet() {
     // modifier clamp.
     const int exponents[] = {-9000, -99, kMinQuarterExponent, 0, kMaxQuarterExponent, 120, 9000};
     for (int e : exponents) {
+        // 260, not 256: m=256..259 wrap modulo uint8_t back to 0..3, re-covering the four
+        // lowest bytes rather than reaching any byte 256 alone couldn't already reach.
         for (int m = 0; m < 260; ++m) {
             const Division d = makeDivision(e, static_cast<DivisionModifier>(m));
             const int index = divisionIndex(d);