Route every extension bank-directory lookup through one bankRootOf seam

The pure bankRootFor(rppPath, unsavedRoot) and the shell bankRootOf(ReaProject*) replace eleven hand-rolled .rpp-parent derivations. No unsaved root is supplied yet, so behaviour and refusals are unchanged. Save-As relocation now reads the stored lastBankRoot_.

src/shell/capture/bake_land.cpp

@@ -13,12 +13,12 @@
 #include <utility>
 #include <vector>
 
-#include "core/capture/capture_paths.h"  // projectDirOfRpp
 #include "core/wire/bake_wire.h"
 #include "core/wire/ext_state_read.h"    // readProjExtStateGrowing (the shared grow loop)
 #include "ext_keys.h"
 #include "shell/capture/bake_landing.h"
 #include "shell/panel/panel_input.h"     // bankPanelRefresh
+#include "shell/persist/bank_root.h"
 #include "shell/persist/session.h"
 #include "shell/undo/undo_block.h"       // the ONE undo-block opener
 
@@ -77,19 +77,17 @@ KeyRead readKey(ReaProject* proj, const std::string& key) {
 
 struct OpenProject {
     ReaProject* proj = nullptr;
-    std::string dir;  // the project's own directory; empty for a never-saved project
+    std::string dir;  // the project's bank root; empty when it has no bank location
 };
 
 // Every open project tab. The request key lives in the INSTANCE's project, which is not
 // necessarily the focused one, so the scan cannot assume the current tab holds it.
 std::vector<OpenProject> openProjects() {
     std::vector<OpenProject> out;
-    std::vector<char> buf(4096, '\0');
     for (int idx = 0;; ++idx) {
-        buf[0] = '\0';
-        ReaProject* proj = EnumProjects(idx, buf.data(), static_cast<int>(buf.size()));
+        ReaProject* proj = EnumProjects(idx, nullptr, 0);
         if (!proj) break;
-        out.push_back(OpenProject{proj, projectDirOfRpp(std::string(buf.data()))});
+        out.push_back(OpenProject{proj, bankRootOf(proj)});
     }
     return out;
 }