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

tests/test_browser_scroll.cpp

@@ -12,6 +12,9 @@
 // and returning every index for an empty query.
 
 #include "../src/core/instrument/ui/browser_scroll.h"
+// The modal reuses the Sample face's chrome metrics (kPad / kTitleHeight); assert against
+// those same constants so a metric change can never desync the sheet from what it covers.
+#include "../src/core/instrument/ui/sample_bands.h"
 
 #include <cstdio>
 #include <string>