[WIP] Fix tooltips on graphs in dashboards

[Copilot]

Thanks for assigning this issue to me. I'm starting to work on it and will keep this PR's description up to date as I form a plan and make progress.

Original issue description:

Problem

Tooltips on graphs within dashboards are not displaying correctly or providing the expected information. This impacts data readability and user interaction.

Steps to Reproduce

1. Open a dashboard containing one or more graphs.
2. Hover over a graph to trigger the tooltip.
3. Observe that the tooltip is missing, incomplete, or displays incorrect data.

Expected Behavior

Tooltips should appear when hovering over graph elements and display relevant information about the data point.

Additional Information

• This issue affects multiple graph types within dashboards.
• A fix should ensure tooltips are consistent across all dashboard graphs.

---

Please investigate the root cause and update the tooltip logic to restore correct functionality.

Fixes #287.

---

✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.

[Copilot]

@glynhudson 👋 This repository doesn't have Copilot instructions. With Copilot instructions, I can understand the repository better, work faster and produce higher quality PRs.

I can generate a .github/copilot-instructions.md file for you automatically. Click here to open a pre-filled issue and assign it to me. I'll write the instructions, and then tag you for review.