Γ-W1-T1 review fixes: mode-independent taper rounding, sharper drag-step test, reset-sweep verifies stored fields

Swap nearbyint for std::round (MXCSR-independent); derive the finest-drag test
from the editor floor, not the knob; verify resets against fields, not norms;
record the spline-point modifier exclusion.

tests/test_deck_values.cpp

@@ -175,8 +175,11 @@ static void testResetLandsOnTheStoredDefaultOfEachControl() {
 // EVERY knob resets to its own stored default, not just the six dual-ring pairs above. Swept
 // over the whole control-id space so a control added later cannot quietly miss the reset table:
 // perturb, reset, and require the control to read exactly what a fresh PlaySeconds reads.
+// Compared against the STORED FIELD directly (deckDoubleField/deckFloatField), not the
+// normalized read-back: deckParamNorm is not guaranteed injective, so a norm match is weaker
+// than the criterion — verification against a default-constructed PlaySeconds.
 static void testEveryKnobIdResetsToItsDefault() {
-    const PlaySeconds defaults;
+    PlaySeconds defaults;
     for (int i = 0; i < static_cast<int>(DeckParam::kCount); ++i) {
         const DeckParam id = static_cast<DeckParam>(i);
         if (deckParamUnit(id) == UnitCategory::None) continue;  // no reset gesture
@@ -184,9 +187,17 @@ static void testEveryKnobIdResetsToItsDefault() {
         PlaySeconds p;
         setDeckParam(id, p, 0.37, 0);
         setDeckParam(id, p, 0.83, 0);  // two writes: one of the two is off every default
-        CHECK(deckParamNorm(id, p) != deckParamNorm(id, defaults));
-        resetDeckParam(id, p);
-        CHECK(deckParamNorm(id, p) == deckParamNorm(id, defaults));
+        if (double* pd = deckDoubleField(id, p)) {
+            CHECK(*pd != *deckDoubleField(id, defaults));
+            resetDeckParam(id, p);
+            CHECK(*pd == *deckDoubleField(id, defaults));
+        } else if (float* pf = deckFloatField(id, p)) {
+            CHECK(*pf != *deckFloatField(id, defaults));
+            resetDeckParam(id, p);
+            CHECK(*pf == *deckFloatField(id, defaults));
+        } else {
+            CHECK(false);  // every non-None, non-excluded id must own a reset field
+        }
     }
 }
 
@@ -279,8 +290,10 @@ static void testAValueStoredUnderTheOldCeilingIsReadNotRewritten() {
     CHECK(p.adsr.releaseSeconds == 2.0);
     CHECK(normDecay > 0.0 && normDecay < 1.0);   // still on the knob, just at a new angle
     CHECK(deckParamNorm(DeckParam::kRelease, p) > normDecay);
-    // And it survives the norm the knob would hand back, so a no-op touch of the control does
-    // not quantize a legacy value away.
+    // And a no-op touch survives the norm the knob would hand back — for THIS value, which is
+    // exactly on the taper's output quantum grid (1.75 s parses to a grid-aligned double). A
+    // legacy value off the grid (e.g. 1.2345678912345) WOULD be re-quantized on first touch;
+    // that is correct, intended behaviour, not a gap this test is claiming to cover.
     setDeckParam(DeckParam::kDecay, p, normDecay, 0);
     CHECK(p.adsr.decaySeconds == 1.75);
 }