S4 Tier 0: the bank plays — VST3 marshals MIDI to the S3 core, reads the live bank + resolves WAV the M4 way, mono downmix, lock-free load handoff, LICE sample-pick

src/capture_paths.h

@@ -121,6 +121,14 @@ std::string bankRelativeForName(const std::string& fileName);
 std::string resolveBankFile(const std::string& projectDir,
                             const std::string& relativePath);
 
+// The project directory that holds a .rpp: its parent directory, forward-slashed,
+// trailing slash stripped. Empty in -> empty out (an unsaved project has an empty
+// .rpp path, which must stay empty so resolveBankFile refuses to resolve — the
+// no-default-location invariant). This is the M4 convention persist uses to place
+// the bank alongside the .rpp; extracted here (pure) so the VST3 instrument resolves
+// audio paths the SAME way persist does rather than re-implementing the derivation.
+std::string projectDirOfRpp(const std::string& rppPath);
+
 // A relocation plan for the physical bank folder on Save-As to a new project
 // location. The index's relative paths do NOT change (they are relative to the
 // project dir, which is what moved with the .rpp), so relocation is purely a