Q-W2 review follow-ups: anon-namespace TU-private panel helpers, fix stale bank_panel.cpp comments, correct shim-transitivity claim

Wraps ~50 file-local helpers across all eight panel TUs in namespace{} (dissolves the menuAppend default-arg ODR trap); zero behavior change, 60/60 green.

src/shell/panel/panel_window.cpp

@@ -46,6 +46,8 @@ PanelState g_panel;
 
 // --- Dialog proc + docking ----------------------------------------------------
 
+namespace {
+
 // Decodes a WM_DROPFILES HDROP into the dropped file paths (absolute, OS-native) and hands
 // them to the S8 ingest path. Multi-file drop: ingestDroppedFiles imports all into the active
 // bank (bank-fill only — no assignment to any live instance). Always DragFinish's the HDROP
@@ -193,6 +195,8 @@ void closePanel() {
     g_panel.open = false;
 }
 
+}  // namespace
+
 }  // namespace reasampler::panel
 
 // --- Public API (the lifecycle seam — panel_window.h) --------------------------