feat: restrict element selection to text elements only

- Remove containers (section, div, article, etc.) from selectable elements
- Remove media elements (img, figure, ul, ol, table) from selection
- Keep text elements: headings, paragraphs, links, formatting tags
- Add figcaption as selectable, remove span

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/App.vue

@@ -236,7 +236,7 @@ const clearSelectedPages = () => {
   selectedPages.value = [];
 };
 
-// Content elements that can trigger ElementPopup
+// Text elements that can trigger ElementPopup (excluding containers, images, etc.)
 const CONTENT_ELEMENTS = [
   'P',
   'H1',
@@ -245,34 +245,17 @@ const CONTENT_ELEMENTS = [
   'H4',
   'H5',
   'H6',
-  'IMG',
-  'FIGURE',
-  'FIGCAPTION',
-  'UL',
-  'OL',
-  'LI',
   'BLOCKQUOTE',
-  'PRE',
+  'LI',
-  'CODE',
-  'TABLE',
-  'THEAD',
-  'TBODY',
-  'TR',
-  'TH',
-  'TD',
   'A',
-  'SPAN',
   'STRONG',
   'EM',
   'B',
   'I',
   'U',
-  'ARTICLE',
+  'CODE',
-  'SECTION',
+  'PRE',
-  'ASIDE',
+  'FIGCAPTION',
-  'HEADER',
-  'FOOTER',
-  'NAV',
 ];
 
 // Check if element is a content element (or find closest content parent)