Support custom metrics on chart x-axis #47
Description
Summary
Allow users to select custom logged metrics (e.g. Epoch) as the x-axis for chart widgets. Currently only "time" and "step" are available as x-axis options.
Motivation
Many ML workflows track progress by epoch or other custom counters rather than raw step count or wall-clock time. Users need the flexibility to plot metrics against any other logged metric.
Desired Behavior
- The x-axis dropdown in chart settings should include all logged metrics (not just "time" and "step")
- This should work both when creating a new widget and when editing an existing one
- Note: the metric selector may already exist in chart edit settings but appears to be missing during widget creation
Current Behavior
X-axis options are limited to "time" and "step". Custom metrics like Epoch cannot be used as the x-axis.
References
- Pylon ticket #363
- Requested by TFC team (Slack, Feb 9 2026)