Fix title extraction to always use filename/directory name instead of content

- Remove H1 and HTML title extraction from parse methods
- Always use formatDisplayName() for consistent filename-based titles
- Add file path parameters to parseMarkdown() and parseHTML()
- Fix directory precedence to check directories before files
- Update AGENTS.md with title vs filename clarification
- Remove debug code from templates and methods

Resolves: Page titles now consistently show file/directory names
without language prefixes and extensions, never content titles.

engine/templates/assets/footer.mustache

@@ -6,7 +6,6 @@
                     <div class="file-info">
                         <i class="bi bi-file-text"></i>
                         <span class="page-title" title="{{page_title}}">{{page_title}}</span>
-                        <!-- DEBUG: Raw title: {{debug_page_title}} -->
                         {{{file_info_block}}}
                     </div>
                     <div class="site-info">