Tooltip Auto decimals are rounding too aggresively for datasets with small changes.

### What happened? When the "Decimals" in the Time Series panel are set to "auto", rounding up of values is extremely aggressive, leading to loss of readability of data on Tooltip. On the screenshots below you can see that there are changes on the time series data and they are pretty substantial, however the value on the tooltip always stay at "0.999" which causes the chart to be unreadable. This issue persists in newest Grafana This also happen with different decimal points(for example rounding to "1.00" or to "10.1" etc. Changing to static decimals is not acceptable in that case because the data depends on selection of variables and may be extremely different. Sometimes the data may be in values of 0.0001, sometimes in values of 10 depending on variables used. <img width="454" height="281" alt="Image" src="https://github.com/user-attachments/assets/9a1030c0-f1f6-47b5-a870-36f700efc294" /> <img width="440" height="291" alt="Image" src="https://github.com/user-attachments/assets/efeed7e2-8c71-45e8-9db2-c2a3d350df5b" /> ### What did you expect to happen? I expect for it to work like in Grafana 6.1.1 which had the "Auto" decimals work flawlessly. <img width="227" height="253" alt="Image" src="https://github.com/user-attachments/assets/f6d32259-8c3f-42a4-856d-a6ebcd39fd89" /> ### Did this work before? It worked in Grafana 6.1.1 extremely well. Had zero problems with that. I jumped all the way to newest Grafana, so I don't know on which version it worked for the last time. ### How do we reproduce it? 1. Get a dataset with values for example between 0.999040 and 0.999060 and show it on Time Series 2. Keep the "decimals" to "auto and keep the Tooltip enabled" 3. Observe the values on the Tooltip For the "Get help" data in next section, I am sorry but I had to remove "original dashboard JSON" panel, however the data is perfectly readable and has the issue I mentioned. ### Is the bug inside a dashboard panel? | Key | Value | |--|--| | Panel | timeseries @ 12.2.1 | | Grafan…