Speed Gauge text overlapping issue

In the Speed Gauge example on the official ECharts editor, the detail text (value and unit) sometimes overlaps with the pointer or gauge frame, especially for larger values. This reduces readability and affects the visual presentation of the gauge.

Expected Behavior:
. The value and unit text should be properly centered and clearly separated from the pointer.
. Text alignment should remain correct for all values within the gauge range.

Steps to Reproduce:

. Open the official editor: https://echarts.apache.org/examples/en/editor.html?c=gauge-speed
. Observe the value displayed in the center of the gauge.
. Notice that the detail text overlaps or is positioned too close to the pointer.

Suggested Improvement:

Adjust the offsetCenter or implement dynamic positioning in the detail property of the gauge.
Ensure text does not overlap with the pointer for any value within the range.

Open the gauge-speed example in the official ECharts editor and inspect its gauge detail configuration, especially offsetCenter. Try values across the gauge range and adjust the positioning so the value and unit remain centered and separated from the pointer and frame.

Written by the indexing model from the issue text.