feat(bank_panel): docked bank grid with LICE waveform thumbnails (M5 Wave A)

Docked SWELL window toggled by a new action, drawing the current bank as
per-sample min/max thumbnails (PCM_source + peaks) with an in-memory cache.
Pure grid-layout/cache-key math in bank_grid (tested). Renames peaks::Sample
-> AudioSample to avoid colliding with bank_model::Sample.

src/main.cpp

@@ -21,6 +21,7 @@
 #include <string>
 
 #include "bank_model.h"
+#include "bank_panel.h"
 #include "capture.h"
 #include "persist.h"
 
@@ -44,6 +45,11 @@ reaper_plugin_info_t*   g_rec   = nullptr;  // REAPER's dispatch struct
 // (user keybindings key off it) — see the prefix note above.
 static int g_cmdCaptureMasterSpike = 0;
 
+// Command id for "ReaSampler: toggle bank panel" (M5). FOREVER-STABLE string.
+// The docked grid window is display-only this wave (Wave A) — the action just
+// shows/hides it; it never captures, inserts, or mutates the bank.
+static int g_cmdToggleBankPanel = 0;
+
 // The persistence session (M4): owns the in-memory BankIndex and bridges it to
 // project ext state. A timer tick drives g_session.poll() to detect project
 // load / Save-As; capture adds Samples to g_session.bank(); after a capture we
@@ -57,6 +63,10 @@ static reasampler::ReaSamplerSession g_session;
 static void OnTimer()
 {
     g_session.poll();
+    // Reflect a live bank change (capture / project load) in the docked grid.
+    // Cheap when the bank is unchanged (a fingerprint compare); repaints only on
+    // an actual change. No-op when the panel is closed.
+    reasampler::bankPanelRefresh();
 }
 
 // Runs the M3 spike: render the time-selection master mix, add the Sample, log.
@@ -107,11 +117,22 @@ static bool OnHookCommand(int command, int /*flag*/)
 {
     if (command == 0) return false;
     if (command == g_cmdCaptureMasterSpike) { RunCaptureMasterSpike(); return true; }
+    if (command == g_cmdToggleBankPanel)    { reasampler::bankPanelToggle(); return true; }
     return false;
 }
 
+// REAPER polls this to render each of OUR actions' checked state in menus/toolbars.
+// Return 1 (on) / 0 (off) for ids we own, -1 for everything else (per the contract).
+static int OnToggleAction(int command)
+{
+    if (command == g_cmdToggleBankPanel)
+        return reasampler::bankPanelIsOpen() ? 1 : 0;
+    return -1;  // not ours / non-toggling
+}
+
 // gaccel storage must outlive registration — REAPER holds the pointer.
 static gaccel_register_t g_accelCaptureMaster{};
+static gaccel_register_t g_accelToggleBankPanel{};
 
 extern "C" REAPER_PLUGIN_DLL_EXPORT int REAPER_PLUGIN_ENTRYPOINT(
     REAPER_PLUGIN_HINSTANCE hInstance, reaper_plugin_info_t* rec)
@@ -123,11 +144,18 @@ extern "C" REAPER_PLUGIN_DLL_EXPORT int REAPER_PLUGIN_ENTRYPOINT(
         if (g_rec)
         {
             g_rec->Register("-timer", (void*)&OnTimer);
+            g_rec->Register("-toggleaction", (void*)&OnToggleAction);
             g_rec->Register("-hookcommand", (void*)&OnHookCommand);
+            g_rec->Register("-gaccel", (void*)&g_accelToggleBankPanel);
+            g_rec->Register("-command_id",
+                            (void*)(REASAMPLER_ACTION_PREFIX "TOGGLE_BANK_PANEL"));
             g_rec->Register("-gaccel", (void*)&g_accelCaptureMaster);
             g_rec->Register("-command_id",
                             (void*)(REASAMPLER_ACTION_PREFIX "CAPTURE_MASTER_SPIKE"));
         }
+        // Destroy the docked window and release cached thumbnails before we drop
+        // the API pointers (DockWindowRemove/DestroyWindow need them live).
+        reasampler::bankPanelShutdown();
         g_rec = nullptr;
         return 0;
     }
@@ -153,9 +181,30 @@ extern "C" REAPER_PLUGIN_DLL_EXPORT int REAPER_PLUGIN_ENTRYPOINT(
         g_accelCaptureMaster.accel.cmd = g_cmdCaptureMasterSpike;
         g_accelCaptureMaster.desc      = "ReaSampler: capture master mix (spike)";
         rec->Register("gaccel", (void*)&g_accelCaptureMaster);
-        rec->Register("hookcommand", (void*)&OnHookCommand);
     }
 
+    // Point the bank panel at the live session BEFORE registering its action, so
+    // a toggle firing immediately has a session to read (M5). Does not open the
+    // window — only stores the session pointer.
+    reasampler::bankPanelInit(&g_session);
+
+    // Register the M5 "toggle bank panel" action (command_id -> gaccel ->
+    // hookcommand + toggleaction for the checked state).
+    g_cmdToggleBankPanel = rec->Register(
+        "command_id",
+        (void*)(REASAMPLER_ACTION_PREFIX "TOGGLE_BANK_PANEL"));
+    if (g_cmdToggleBankPanel)
+    {
+        g_accelToggleBankPanel.accel.cmd = g_cmdToggleBankPanel;
+        g_accelToggleBankPanel.desc      = "ReaSampler: toggle bank panel";
+        rec->Register("gaccel", (void*)&g_accelToggleBankPanel);
+        rec->Register("toggleaction", (void*)&OnToggleAction);
+    }
+
+    // One hookcommand routes every ReaSampler action (spike + toggle). Registered
+    // once, after both command ids are minted.
+    rec->Register("hookcommand", (void*)&OnHookCommand);
+
     // Drive project-load / Save-As detection (M4 persist). The timer polls the
     // active project each tick; on a project load it reloads the bank from ext
     // state, on a Save-As it relocates the bank folder under the new .rpp.