Retire the zone system: one capture = one parameter set, and re-seam the engine and Sample face into bands

tests/test_instrument_drop.cpp

@@ -116,7 +116,8 @@ static void testPresetRoundTripsThroughInstrumentReader() {
 
     const ComponentState cs = deserializeComponentState(p.compChunk, kRate);
     CHECK(cs.selectionId == id);          // the capture IS selected — the whole point
-    CHECK(cs.map.zones.empty());          // a drop selects one capture, authors no zones
+    // A drop selects one capture and leaves the parameter set at its defaults.
+    CHECK(!cs.params.rootOverride && !cs.params.loopOverride && !cs.params.startPoint);
     CHECK(cs.channelMode == ChannelMode::Mono);           // fresh-instance default
     CHECK(cs.lastConsumedAssignGeneration == 0);          // fresh instance, no consumed assign
 }
@@ -158,7 +159,7 @@ static void testEmptyIdYieldsEmptyState() {
     CHECK(!p.compChunk.empty());  // still a versioned envelope, just an empty selection
     const ComponentState cs = deserializeComponentState(p.compChunk, kRate);
     CHECK(cs.selectionId.empty());
-    CHECK(cs.map.zones.empty());
+    CHECK(!cs.params.rootOverride && !cs.params.loopOverride && !cs.params.startPoint);
 }
 
 // Deterministic: the same id always produces the same bytes (no time/random in the path).