demo time-based: porta el patro de CCAE (multi-set, index = elapsed_s*60, % size per safe loop), substitueix demo.bin per demo1/2/3.bin

source/core/system/demo.cpp

@@ -0,0 +1,17 @@
+#include "core/system/demo.hpp"
+
+#include <cstring>  // for memcpy
+
+// Desempaqueta un blob binari amb TOTAL_DEMO_DATA registres consecutius
+// de DemoKeys (struct POD de 6 bytes). Si el blob no te la mida esperada,
+// torna un vector buit perque el playback el detecti i no peti.
+auto loadDemoDataFromBytes(const std::vector<uint8_t> &bytes) -> DemoData {
+    DemoData dd;
+    const size_t EXPECTED = sizeof(DemoKeys) * TOTAL_DEMO_DATA;
+    if (bytes.size() < EXPECTED) {
+        return dd;
+    }
+    dd.resize(TOTAL_DEMO_DATA);
+    std::memcpy(dd.data(), bytes.data(), EXPECTED);
+    return dd;
+}