Remove stale theme entries in CSSTheme.updateResources (#4291)

Fixed #2698

When updating theme resources from CSS, if a property is removed from the CSS, it should be removed from the generated resource file. Previously, removed properties would persist as stale entries.

This change introduces a cleanup step in `updateResources` that iterates over modified UIIDs and removes all existing theme properties associated with them before applying the new properties from the CSS. A helper method `isOwnedBy` ensures that only properties strictly belonging to the UIID (and its states) are removed, preventing accidental deletion of unrelated properties even if UIIDs contain dots.

Co-authored-by: google-labs-jules[bot] <161369871+google-labs-jules[bot]@users.noreply.github.com>

Author: google-labs-jules[bot]

CodenameOneDesigner/src/com/codename1/designer/css/CSSTheme.java

@@ -1667,9 +1667,42 @@ public Map<String, CacheStatus> calculateSelectorCacheStatus(File cachedFile) th
 
     }
 
+    private boolean isOwnedBy(String key, String id) {
+        if (key.length() <= id.length() + 1) {
+            return false;
+        }
+        if (!key.startsWith(id)) {
+            return false;
+        }
+        char sep = key.charAt(id.length());
+        if (sep != '.' && sep != '#') {
+            return false;
+        }
+        // Check for dots in the suffix
+        return key.indexOf('.', id.length() + 1) == -1;
+    }
+
     public void updateResources() {
-        // TODO:  We need to remove stale theme entries
-        // https://github.com/codenameone/CodenameOne/issues/2698
+        if (res != null) {
+            Map<String, Object> themeData = res.getTheme(themeName);
+            if (themeData != null) {
+                Set<String> keys = new HashSet<String>(themeData.keySet());
+                Set<String> modifiedIds = new HashSet<String>();
+                for (String id : elements.keySet()) {
+                    if (isModified(id)) {
+                        modifiedIds.add(id);
+                    }
+                }
+
+                for (String id : modifiedIds) {
+                    for (String key : keys) {
+                        if (isOwnedBy(key, id)) {
+                             res.setThemeProperty(themeName, key, null);
+                        }
+                    }
+                }
+            }
+        }
 
         for (String id : elements.keySet()) {
             if (!isModified(id)) {