Add a description for panel query legend

<!-- Please only use this template for submitting feature requests --> **Why is this needed**: Some query name are not self explanatory and requires an explanation. A queryeryc description as a tooltip would go a long way for explaining what the query represents while not bloating the panel. **What would you like to be added**: Panels have a description which is displayed as a tooltip when hovering the `ⓘ` symbol next to the panel's title. <img width="744" height="580" alt="Image" src="https://github.com/user-attachments/assets/52e1a6fc-2cee-4202-88d2-def93c7894d6" /> I would to the exact same thing for queries. If a query description is provided, a `ⓘ` symbol would be displayed next to the query legend name and the provided description would appear in a tooltip. <img width="744" height="580" alt="Image" src="https://github.com/user-attachments/assets/c3f2d8e0-457b-4fa2-ac0e-cb84abbb3cbd" /> **Who is this feature for?** [Add information on what kind of user the feature is for.]