Dashboards: Ad-Hoc Filter regex pattern displays HTML entities instead of special characters

### What happened? When using Ad-Hoc Filters in Grafana Explore with a regex pattern containing special characters, the filter displays HTML-encoded entities (e.g., `&#x2F;`, `*MCDN`, `.*`) instead of the actual characters in the suggestion tooltip. <img width="584" height="136" alt="Image" src="https://github.com/user-attachments/assets/feb602f2-a145-44ff-b8b2-f0833796d6ca" /> The filter input shows the regex pattern correctly as `!~ /.*MCDN.*/`, but when hovering or interacting with the filter suggestions, the tooltip shows escaped HTML entities instead of the actual special characters. ### What did you expect to happen? The Ad-Hoc Filter suggestion should display the regex pattern with proper special characters: `"Use custom value: /.*MCDN.*"` without HTML entity escaping. ### Did this work before? Unknown - I don't know which version of Grafana this worked in, or if it ever worked. ### How do we reproduce it? 1. Navigate to Grafana Explore 2. Add an Ad-Hoc Filter with any field (e.g., `study.description.id`) 3. Select the "not regex match" (`!~`) operator 4. Enter a regex pattern containing special characters, such as `/.*MCDN.*/` 5. Observe the suggestion tooltip that appears 6. Notice that the tooltip displays HTML entities (`&#x2F;`, `&#x2A;`) instead of the actual characters (`/`, `*`) ### Is the bug inside a dashboard panel? No, this occurs in the Explore view's Ad-Hoc Filter interface. ### Environment (with versions)? Grafana: 12.3.0-enterprise OS: macOS Browser: Chrome 142 ### Grafana platform? Docker ### Datasource(s)? _No response_