Replace the debug breakpoint with a warning-log when a single-bar
null-segment is detected in `get_null_segs()`. This lets the gap
analysis continue while still alerting about the anomaly.
Deats,
- extract the 3-bar window (before, null, after) and calculate
a `gap: pendulum.Interval` for the warning msg.
- comment-out the old breakpoint block for optional debugging as needed.
(this commit msg was generated in some part by [`claude-code`][claude-code-gh])
[claude-code-gh]: https://github.com/anthropics/claude-code