Improve behaviour of nuclide name enter on "Reference Photopeak" tab.

May be solution for issue #19 - but not checked on Linux/Windows yet.
Fixed if you type a nuclide in fast and hit enter, the first item in suggested list would be entered (before it was updated from the C++), instead of what you typed.
Fix erroneous error message when clicking on a suggestion from the list (the error message would say what you had typed so far was an invalid nuclide)
Hopefully fixed special character handling - like the "(" not entering sometimes when trying to add a reaction.
Fix selection not being visible when you use arrow to go down past visible list (when scrollbar is present).
Improve handling width of suggestion popup - hopefully.

Author: wcjohns

InterSpec/IsotopeNameFilterModel.h

@@ -44,6 +44,7 @@ namespace SandiaDecay
 
 namespace Wt
 {
+  class WLineEdit;
   class WSuggestionPopup;
 }
 
@@ -113,6 +114,19 @@ class IsotopeNameFilterModel : public  Wt::WAbstractItemModel
   //  we will do a hack to catch this.
   static void setQuickTypeFixHackjs( Wt::WSuggestionPopup *popup );
 
+  //Fixes multiple issues with WSuggestionPopup:
+  //  1. Race condition: when user types quickly and hits Enter, the suggestion popup
+  //     may not have filtered yet, causing wrong suggestion to be selected. This
+  //     intercepts Enter key and checks if typed text exactly matches any suggestion,
+  //     using that match instead of the highlighted one.
+  //  2. Arrow key navigation: ensures arrow key selection works correctly when hitting Enter.
+  //  3. Mouse click handling: prevents premature change events when clicking suggestions,
+  //     ensuring only the final suggestion value triggers a change event.
+  //  4. Popup hiding: automatically hides the suggestion popup when values are entered.
+  //  5. Special character input: allows special characters like "(" to be entered without
+  //     being blocked by the suggestion popup.
+  static void setEnterKeyMatchFixJs( Wt::WSuggestionPopup *popup, Wt::WLineEdit *edit );
+  
   /** By default nuclides are included in suggestions, this function allows
    * disabling/enabling this.
    */

InterSpec_resources/InterSpec.css

@@ -1698,3 +1698,20 @@ a:hover { color:#E88400; border-bottom:none; }
   flex-direction: row;
   align-items: center;
 }
+
+/* Style nuclide suggestion popup list items to be wider and full-width for easier clicking */
+.nuclide-suggest
+{
+  min-width: 80px; /* Ensure popup is at least as wide as the list items */
+  overflow-x: hidden; /* Prevent horizontal scrollbar when vertical scrollbar appears */
+}
+
+.nuclide-suggest li,
+.nuclide-suggest .Wt-suggest-item
+{
+  min-width: 80px;
+  width: 100%;
+  padding-left: 5px;
+  padding-right: 5px;
+  box-sizing: border-box; /* Include padding in width calculation */
+}