Heatmap Visualization: Distorted data when few datapoints/rows present

### What happened? I have been using the heatmap visualization to implement a utilization heatmap, and it has performed mostly well in this regard except for a the case where only a few datapoints/rows are present. The X axis will display the correct range for the time selected, but the datapoint rectangles will appear stretched or entirely missing, despite being present when switching to table mode. This bug seems to be driven by the number of rows visible on the heatmap. When that number goes low, the visible datapoints remaining are distorted. This bug appears when tested from both Firefox and Brave browser Enabling 'Calculate from data' causes the bug to no longer present (#103051 related?) ### What did you expect to happen? I would expect the datapoints to remain visible in the correct X/Y positions with correct dimensions for the axes, not stretched or invisible, regardless of the number of other rows visible. ### Did this work before? I have not used the heatmap this way before. ### How do we reproduce it? 1. Create a new dashboard from the provided JSON, ensuring correct time range and UTC time zone 2. Run the provided query and observe the correct data presentation. 3. Comment out between 1 and all of the out-of-view datapoints in the query, and rerun the query. As more are commented, observe a greater distorting effect which occurs with the in-view datapoints, up to their complete disappearance. 4. Once all out-of-view datapoints are commented out and the panel is empty, switch to table mode to confirm the datapoints are still present underneath, just not visible. 5. Switch off table mode, and enable 'Calculate from data' 6. Rerun the query, and observe that in-view data presents properly Video example: https://github.com/user-attachments/assets/9aeaff61-e2d3-45c1-adc3-ccd37bdbc811 ### Is the bug inside a dashboard panel? | Key | Value | |--|--| | Panel | heatmap @ 12.1.1 | | Grafana | Grafana v12.1.1 (df5de8219b) // Open Source | <details><summary>Panel d…