Q-W1 pt2: core/shell/app relocation + sub-namespaces; one concrete ui::Rect (LTRB fork retired); slot_map split from bank_book; BankIndex→BankModel; 59/59 green

src/core/instrument/map/bridge_marshal.cpp

@@ -0,0 +1,16 @@
+// bridge_marshal.cpp — see bridge_marshal.h. Pure; no host types.
+
+#include "core/instrument/map/bridge_marshal.h"
+
+namespace reasampler::instrument::map {
+
+std::optional<std::string> decodeGetProjExtState(int apiReturn,
+                                                 const std::string& buffer) {
+    // REAPER returns the length of the stored value; 0 means the key is absent. Guard
+    // both the return AND the buffer: a caller that reused a dirty buffer must not
+    // surface stale bytes as a value when the API reported nothing.
+    if (apiReturn <= 0 || buffer.empty()) return std::nullopt;
+    return buffer;
+}
+
+}  // namespace reasampler::instrument::map