fix(bank_panel): arm drag from unselected cell in one gesture

Plain press on an unselected grid cell now commits the single-cell
selection immediately and arms the drag, so moving past the threshold
begins a drag without a prior selecting click. Already-selected and
ctrl/shift paths are unchanged.

src/bank_panel.cpp

@@ -2001,21 +2001,34 @@ void handleClick(int x, int y) {
         return;
     }
 
-    // If the pressed cell is already SELECTED and no modifier is held, arm a drag —
-    // the actual selection change is deferred to LBUTTONUP if no drag begins (so a
-    // plain click on a multi-selection can start a drag without collapsing it first).
-    // Otherwise apply the click immediately. This is the M5-multi-select-drag
-    // disambiguation: M5 has no cell drag; a drag here begins only from a selected
-    // cell past a movement threshold (see onMouseMove), so plain click/shift/ctrl
-    // multi-select is untouched.
+    // Drag-arm disambiguation for plain (no ctrl, no shift) presses on a grid cell:
+    //
+    // • Already-selected cell: defer the selection change to LBUTTONUP so a plain
+    //   press on a multi-selection doesn't collapse it before we know whether a drag
+    //   will happen. Arm the drag with the current (multi-)selection as the payload
+    //   candidate; only the caret moves immediately.
+    //
+    // • Unselected cell: apply the plain-click selection immediately (collapses to
+    //   the single pressed cell) THEN arm a drag from it — so the user can press-and-
+    //   drag in one gesture without a prior selecting click. The selection is set
+    //   before arming so that focusedSelectionIds() resolves the right payload when
+    //   the threshold is crossed in onMouseMove.
+    //
+    // ctrl / shift presses are selection-only gestures — no drag arm in either case.
     const bool onSelected = g_panel.selection.contains(hit);
-    if (onSelected && !ctrlDown() && !shiftDown()) {
+    if (!ctrlDown() && !shiftDown()) {
+        if (!onSelected) {
+            // Commit the single-cell selection now so the drag payload is correct.
+            g_panel.selection = applyClick(g_panel.selection, hit, false, false, count);
+            g_panel.selItemCount = count;
+        } else {
+            // Move the caret to the pressed cell; defer collapsing multi-selection.
+            g_panel.selection.focus = hit;
+        }
         g_panel.dragArmed = true;
         g_panel.dragStartX = x;
         g_panel.dragStartY = y;
         g_panel.dragSourceRegion = reg;
-        // Keep the current (multi-)selection as the drag payload candidate.
-        g_panel.selection.focus = hit;  // move the caret to the pressed cell
         invalidatePanel();
         return;
     }