refactor(bank_panel): factor resetDragState() helper; fix WM_CAPTURECHANGED missing instrumentDropTrack reset

All eight drag-state fields cleared through one canonical helper.
WM_CAPTURECHANGED now resets instrumentDropTrack (was missing per doc-contract).
WM_DESTROY and closePanel gain dropKind/dropBankId resets (inert on teardown; correct for symmetry).

src/bank_panel.cpp

@@ -3035,6 +3035,20 @@ void doReplaceDrop(const std::string& newId, const std::string& oldId,
     invalidatePanel();
 }
 
+// Clears all drag-state fields to their resting values. Called from every exit path
+// (button-up, WM_CAPTURECHANGED, WM_DESTROY, closePanel) so the set of cleared fields
+// stays consistent across all four sites.
+void resetDragState() {
+    g_panel.dragArmed = false;
+    g_panel.dragging = false;
+    g_panel.dropKind = DropKind::None;
+    g_panel.dropBankId.clear();
+    g_panel.cardGesture = CardGesture::None;
+    g_panel.dragTargetSlot = -1;
+    g_panel.dragPrimaryId.clear();
+    g_panel.instrumentDropTrack = nullptr;
+}
+
 // Commits (or abandons) a drag on button-up. The resolved pure CardGesture decides:
 //   * Reorder / Replace -> in-grid, within the source bank (L7); one Ctrl-Z each.
 //   * Move / Copy       -> the EXISTING cross-bank transfer (unchanged; Ctrl = copy).
@@ -3095,14 +3109,7 @@ void onLBtnUp(int x, int y) {
         if (focus >= 0)
             g_panel.selection = applyClick(g_panel.selection, focus, false, false, count);
     }
-    g_panel.dragArmed = false;
+    resetDragState();
-    g_panel.dragging = false;
-    g_panel.dropKind = DropKind::None;
-    g_panel.dropBankId.clear();
-    g_panel.cardGesture = CardGesture::None;
-    g_panel.dragTargetSlot = -1;
-    g_panel.dragPrimaryId.clear();
-    g_panel.instrumentDropTrack = nullptr;  // S17: clear the FX hotspot after the release
     invalidatePanel();
 }
 
@@ -3199,13 +3206,7 @@ WDL_DLGRET dlgProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam) {
             // state lingers, mirroring onLBtnUp's reset (peer-path symmetry). Nothing is
             // mutated on a cancel; the cursor is restored to the arrow.
             if (g_panel.dragArmed || g_panel.dragging) {
-                g_panel.dragArmed = false;
+                resetDragState();
-                g_panel.dragging = false;
-                g_panel.dropKind = DropKind::None;
-                g_panel.dropBankId.clear();
-                g_panel.cardGesture = CardGesture::None;
-                g_panel.dragTargetSlot = -1;
-                g_panel.dragPrimaryId.clear();
                 SetCursor(LoadCursor(nullptr, IDC_ARROW));
                 invalidatePanel();
             }
@@ -3227,11 +3228,7 @@ WDL_DLGRET dlgProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam) {
             if (GetCapture() == hwnd) ReleaseCapture();
             stopAudition();
             g_panel.selection = Selection{};
-            g_panel.dragArmed = g_panel.dragging = false;
+            resetDragState();
-            g_panel.cardGesture = CardGesture::None;
-            g_panel.dragTargetSlot = -1;
-            g_panel.dragPrimaryId.clear();
-            g_panel.instrumentDropTrack = nullptr;  // S17: drop the FX hotspot on teardown
             g_panel.hovered = Hover{};
             g_panel.tooltipShown = false;
             g_panel.hwnd = nullptr;
@@ -3288,8 +3285,7 @@ void closePanel() {
     if (GetCapture() == g_panel.hwnd) ReleaseCapture();
     stopAudition();
     g_panel.selection = Selection{};
-    g_panel.dragArmed = g_panel.dragging = false;
+    resetDragState();
-    g_panel.instrumentDropTrack = nullptr;  // S17: drop the FX hotspot on close
     unregisterAccel();
     if (g_panel.hwnd) {
         DockWindowRemove(g_panel.hwnd);