Resolve ReaSampler 9000 samples against the instance's own project, not the focused tab

sampleRoots matches getReaperParent(3) among EnumProjects' open projects; every instrument sample read goes through an ordered root list (one root today) so a later temp-bank root slots in after it.

src/core/instrument/map/sample_roots.cpp

@@ -0,0 +1,34 @@
+// sample_roots.cpp — see sample_roots.h.
+
+#include "core/instrument/map/sample_roots.h"
+
+#include "core/capture/capture_paths.h"  // projectDirOfRpp / resolveBankFile (persist's convention)
+
+namespace reasampler::instrument::map {
+
+std::string ownProjectDir(const void* own, const std::vector<ProjectTab>& open) {
+    if (!own) return {};
+    for (const ProjectTab& tab : open) {
+        if (tab.project == own) return capture::projectDirOfRpp(tab.rppPath);
+    }
+    return {};
+}
+
+std::vector<std::string> sampleRootCandidates(const std::string& projectDir) {
+    if (projectDir.empty()) return {};
+    return {projectDir};
+}
+
+std::vector<std::uint8_t> readFromFirstRoot(const std::vector<std::string>& roots,
+                                            const std::string& relativePath,
+                                            const FileReader& read) {
+    for (const std::string& root : roots) {
+        const std::string abs = capture::resolveBankFile(root, relativePath);
+        if (abs.empty()) continue;
+        std::vector<std::uint8_t> bytes = read(abs);
+        if (!bytes.empty()) return bytes;
+    }
+    return {};
+}
+
+}  // namespace reasampler::instrument::map