Add hover tooltips for truncated sidebar titles

Section and lesson names in the course-outline sidebar/tree get
clipped with an ellipsis when they don't fit - a title attribute now
shows the full text on hover.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

templates/_course_tree.html

@@ -22,7 +22,7 @@
     <div class="tree-header directory" onclick="toggleTree(this)">
         <div class="tree-title">
             <span class="tree-icon">{{ icons.icon('folder', 16) }}</span>
-            <span class="tree-name">{{ node.name }}</span>
+            <span class="tree-name" title="{{ node.name }}">{{ node.name }}</span>
             <span class="tree-stats">
                 {% if stats.total_lessons %}{{ stats.completed_lessons }}/{{ stats.total_lessons }} watched{% else %}Empty{% endif %}
             </span>
@@ -52,7 +52,7 @@
                     {% elif lesson.lesson_type == 'mixed' %}{{ icons.icon('package', 16) }}
                     {% else %}{{ icons.icon('file-text', 16) }}{% endif %}
                 </span>
-                <span class="lesson-name">{{ lesson.title }}</span>
+                <span class="lesson-name" title="{{ lesson.title }}">{{ lesson.title }}</span>
             </div>
             <div class="lesson-meta">
                 <span class="lesson-type {{ lesson.lesson_type }}">{{ lesson.lesson_type|title }}</span>