1639: Fix assertion error and improve line marker immutability

Addressed an assertion failure related to improper `PsiElement` usage for popup models in `PluginLineMarkerProvider`. Made the `NavigationGutterIconBuilder` instance immutable by declaring it as `final`, enhancing code safety and readability. Updated the changelog for relevant changes.

Author: VitaliyBoyko

CHANGELOG.md

@@ -12,6 +12,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0).
   Replaced hardcoded Magento versions with dynamic fetching via Packagist API.
   Fixed UI icon references.
   Updated Run command.
+- java.lang.Throwable: Assertion failed: Do not use PsiElement for popup model. See PsiTargetNavigator [#2485](https://github.com/magento/magento2-phpstorm-plugin/pull/2485)
 
 ### Changed
 

src/main/java/com/magento/idea/magento2plugin/linemarker/php/PluginLineMarkerProvider.java

@@ -71,7 +71,7 @@ public void collectSlowLineMarkers(
 
                 if (!results.isEmpty()) {
                     // Add the property to a collection of line marker info
-                    NavigationGutterIconBuilder<PsiElement> builder =
+                    final NavigationGutterIconBuilder<PsiElement> builder =
                             NavigationGutterIconBuilder.create(AllIcons.Nodes.Plugin)
                                     .setTargets(results)
                                     .setTooltipText(TOOLTIP_TEXT);