Hybrid Markdown editor: HTML tags (<details>, <summary>, <kbd>) are not rendered

Does this issue occur when all extensions are disabled?: Yes

- VS Code Version: 1.132.0 (Universal), commit df53daabb18cd157bdb08c7f01c34df936cf12f4
- OS Version: macOS Darwin arm64 25.1.0

Feature: Hybrid Markdown editor (Experimental), enabled via `workbench.editor.markdownDefaultEditorInAgentsWindow`

Steps to Reproduce:

1. Set `workbench.editor.markdownDefaultEditorInAgentsWindow: true` and open a `.md` file containing HTML tags such as ``, ``, or `` in the Hybrid Markdown Editor (`vscode.markdown.editor`).
2. Observe the rendering in both Editing and Reading/Locked modes.

Expected:
Standard HTML tags like ``/`` (collapsible sections) and `` (keyboard shortcut styling) are parsed and rendered as interactive or styled components, matching the built-in Markdown preview behavior.

Actual:
Raw HTML tags (``, ``, ``) are displayed as unrendered plain text.

### Screenshots
**Editing Mode**

**Preview / Locked Mode**