workspace: Use markdown to render LSP notification content (#44215)

Closes #43657

Release Notes:

- Improved LSP notification messages by adding markdown rendering with
clickable URLs, inline code, etc.

<table>
  <tr>
    <td>Before</td>
    <td>After</td>
  </tr>
  <tr>
<td><img width="408" height="153" alt="screenshot-notification-before"
src="https://github.com/user-attachments/assets/53b026de-335f-4c39-937f-590c3b7ea571"
/></td>
<td><img width="408" height="153" alt="screenshot-notification-after"
src="https://github.com/user-attachments/assets/9d6a7baa-8304-4a52-a5d0-0bacf7ea69f9"
/></td>
  </tr>
</table>

---------

Co-authored-by: Danilo Leal <daniloleal09@gmail.com>

Cargo.lock

@@ -20101,6 +20101,7 @@ dependencies = [
  "itertools 0.14.0",
  "language",
  "log",
+ "markdown",
  "menu",
  "node_runtime",
  "parking_lot",