fix: TimeSeries disappearing series lines on zoom

[raworks-software]

Reason for change

This PR fixes a TimeSeries rendering issue where some channels disappear while zooming, and the rendered SVG <path> ends up with an empty d="" attribute.

Observed behavior:

• while zooming into a narrow range, some series become invisible
• in DevTools, the corresponding SVG path is rendered as <path ... d=""></path>

This appears related to:

• Fixes Issue with timeseries rendering #2900
• Fixes Missing data display in time series #1752

Root cause:

• the zoomed line rendering path could be built from sparse/optimized slices that did not contain enough valid points for the current visible range
• when that happened, the D3 line generator produced an empty path

Solution:

• preserve the full filtered series for each channel
• build the zoom-visible segment from the full channel series instead of relying on pre-sliced zoom buckets
• include neighboring boundary points around the visible range so narrow zoom windows still produce a valid line segment
• add guards for degenerate Y-scaling cases and invalid numeric values

What changed

In TimeSeriesVisualizer.jsx:

• store channel.fullSeries for each channel
• add channel.getVisibleSegment(...) to derive the visible segment from the full series using a bisector
• render the zoomed path from channel.fullSeries instead of this.slices[left/right]
• guard Y-scale recalculation against null / non-finite values and flat segments

In Channel.jsx:

• include related multiaxis handling changes so the visualizer receives the expected set of channels when rendering shared charts

Screenshots / Representation

before.mp4

after.mp4

Rollout strategy

No feature flag.
This is a direct bug fix to TimeSeries rendering behavior.

Testing

Manual verification performed locally:

• opened a TimeSeries project with affected data
• zoomed repeatedly into narrow ranges where some channels previously disappeared
• checked the rendered SVG in DevTools
• verified that the affected paths no longer collapse to d="" in the tested cases

Additional validation performed:

• confirmed that normal non-zoomed rendering still works
• confirmed that the code still handles optimized/full-series switching
• confirmed that narrow visible windows still render using boundary points from the full series

Risks

Low to moderate.

Potential risks:

• slight performance impact during zoom because the visible segment is now derived from the full channel series instead of relying entirely on sparse slices
• edge-case behavior may change for extremely large datasets with many channels
• multiaxis behavior should be reviewed carefully because channel aggregation affects shared rendering paths

Risk mitigations:

• only a small visible segment is extracted from the full series
• optimized rendering is still used outside the narrow zoom-path case
• changes are limited to TimeSeries rendering logic

Reviewer notes

The most important logic is in:

• initializeChannel(...)
• setChannelRangeWithScaling(...)

Please review:

• how channel.fullSeries is constructed
• how channel.getVisibleSegment(...) selects boundary points
• the switch away from rendering zoom paths from this.slices[left/right]

General notes

This fix targets the specific failure mode where D3 receives too few valid points for the current visible range and emits an empty SVG path.

The intended behavior after this change is:

• channels remain visible while zooming
• the SVG path for visible data remains valid
• narrow zoom ranges still render a line if neighboring points exist

Overall fixes performed by ChatGPT, I barely did any review of source code.

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