feat(prune): R2 dry-run prune shell + persist wiring, report-only

Add ReaSamplerSession::pruneDryRun enumerating the resolved current bank
folder, feeding the R1 core, and returning a PruneReport (count/bytes/list).
New pure bankRelativeForName + buildPruneReport keep spelling and tally
testable. Register forever-stable BANK_PRUNE_FOLDER action, report-only. No deletion.

src/actions.cpp

@@ -451,6 +451,10 @@ constexpr const char* kIdBankCopySel      = "BANK_COPY_SELECTED";
 constexpr const char* kIdBankRemoveSel    = "BANK_REMOVE_SELECTED";
 constexpr const char* kIdBankPoolFull     = "BANK_POOL_FULLHEIGHT";
 constexpr const char* kIdBankBanksFull    = "BANK_BANKS_FULLHEIGHT";
+// Phase R (Reclaim), R2: the FOREVER-STABLE "Prune bank folder" id. Registered NOW so
+// in-DAW dry-run verification is possible; R2 behaviour is REPORT-ONLY (no deletion),
+// and R3 extends the confirm-and-delete step behind this SAME id — never a throwaway id.
+constexpr const char* kIdBankPruneFolder  = "BANK_PRUNE_FOLDER";
 
 int g_cmdBankCreate = 0;
 int g_cmdBankRename = 0;
@@ -463,6 +467,7 @@ int g_cmdBankCopySel = 0;
 int g_cmdBankRemoveSel = 0;
 int g_cmdBankPoolFull = 0;
 int g_cmdBankBanksFull = 0;
+int g_cmdBankPruneFolder = 0;
 
 gaccel_register_t g_accelBankCreate{};
 gaccel_register_t g_accelBankRename{};
@@ -475,6 +480,7 @@ gaccel_register_t g_accelBankCopySel{};
 gaccel_register_t g_accelBankRemoveSel{};
 gaccel_register_t g_accelBankPoolFull{};
 gaccel_register_t g_accelBankBanksFull{};
+gaccel_register_t g_accelBankPruneFolder{};
 
 // Persists the book after a bank mutation. Mirrors the CAPTURE path (main.cpp
 // RunCapture), NOT the Design-View path: a bank change is held in-session and written
@@ -791,6 +797,31 @@ void doBankRemoveSelected() {
     if (removed > 0) persistBankOp("ReaSampler: remove sample(s)");
 }
 
+// Prune bank folder — Phase R (Reclaim), R2: REPORT-ONLY dry run. Asks the session for
+// the orphan set of the resolved CURRENT bank folder ((owned ∩ present) − referenced,
+// unioned across every bank) and prints the truthful reclaim report — count, reclaimable
+// bytes, and the file list. DELETES NOTHING, writes no ext-state, opens no undo point
+// (pruneDryRun is read-only across the persist seam). R3 extends this SAME action id to
+// confirm-and-delete behind the dry-run guardrail; the report path here is what R3 wraps.
+void doBankPruneFolder() {
+    const PruneReport report = g_session->pruneDryRun();
+
+    if (report.count == 0) {
+        ShowConsoleMsg("ReaSampler prune (dry run): no orphaned files to reclaim.\n");
+        return;
+    }
+
+    std::string msg = "ReaSampler prune (dry run): " + std::to_string(report.count) +
+                      " orphaned file(s), " + std::to_string(report.totalBytes) +
+                      " bytes reclaimable. (Dry run -- nothing deleted.)\n";
+    for (const std::string& rel : report.orphans) msg += "  " + rel + "\n";
+    if (report.truncated) {
+        msg += "  ... (" + std::to_string(report.count - report.orphans.size()) +
+               " more not shown)\n";
+    }
+    ShowConsoleMsg(msg.c_str());
+}
+
 }  // namespace
 
 // Persists a completed bank-index verb as a SINGLE batched REAPER undo point (R-B) —
@@ -851,6 +882,10 @@ void bankRegisterActions(reaper_plugin_info_t* rec, ReaSamplerSession* session)
                                        "toggle pool full-height");
     g_cmdBankBanksFull = registerAction(rec, kIdBankBanksFull, g_accelBankBanksFull,
                                         "toggle banks full-height");
+    // Phase R, R2: the "Prune bank folder" action (report-only in this wave; R3 extends
+    // the confirm-and-delete step behind this SAME forever-stable id).
+    g_cmdBankPruneFolder = registerAction(rec, kIdBankPruneFolder, g_accelBankPruneFolder,
+                                          "prune bank folder");
 }
 
 bool bankHandleCommand(int command) {
@@ -867,6 +902,7 @@ bool bankHandleCommand(int command) {
     if (command == g_cmdBankRemoveSel)    { doBankRemoveSelected(); return true; }
     if (command == g_cmdBankPoolFull)     { bankPanelToggledPoolFullHeight(); return true; }
     if (command == g_cmdBankBanksFull)    { bankPanelToggledBanksFullHeight(); return true; }
+    if (command == g_cmdBankPruneFolder)  { doBankPruneFolder(); return true; }
 
     return false;  // not ours — caller's hookcommand keeps looking
 }
@@ -874,6 +910,8 @@ bool bankHandleCommand(int command) {
 void bankUnregisterActions(reaper_plugin_info_t* rec) {
     // Mirror-unregister with '-'-prefixed strings, reverse of registration order. Each
     // '-command_id' re-presents the same interned channel-qualified id (channelIdFor).
+    rec->Register("-gaccel", (void*)&g_accelBankPruneFolder);
+    rec->Register("-command_id", (void*)channelIdFor(kIdBankPruneFolder));
     rec->Register("-gaccel", (void*)&g_accelBankBanksFull);
     rec->Register("-command_id", (void*)channelIdFor(kIdBankBanksFull));
     rec->Register("-gaccel", (void*)&g_accelBankPoolFull);