[davrens101]

Prevent internal _template leak into layout rangeslider opp-axis

Fixes #6310.

When an axis with a rangeslider autoranges in doAutoRange (src/plots/cartesian/autorange.js), axeRangeOpts for each opposing axis is copied back into anchorAx._input.rangeslider[ax._name]. Because axeRangeOpts is instantiated via Template.newContainer in rangeslider/defaults.js, it contains an internal _template property (either null or a template object). Copying the whole object into anchorAx._input pollutes the user-facing layout object with _template: null under rangeslider[yaxis].

This non-schema property causes serialization and validation failures in downstream consumers such as Dash Python (ValueError: Invalid property specified for object of type plotly.graph_objs.layout.xaxis.rangeslider.YAxis: '_template').

Solution

Delete _template from the copied options object before assigning back to anchorAx._input.rangeslider[ax._name]. The internal _template property remains intact on _fullLayout as expected.

Regression coverage

Added two unit tests in test/jasmine/tests/range_slider_test.js:

1. should not leak _template into input layout rangeslider opp-axis container
2. should not leak _template into input layout when a template is used

Prior to the fix:
expect(gd.layout.xaxis.rangeslider.yaxis._template).toBeUndefined() failed with Error: Expected null to be undefined.

With the fix:
Both tests pass cleanly. template_test.js passes 14 of 14 tests. Biome linter passes without warnings.

Review and disclosure

AI assisted the patch, regression tests, and PR description. Verified against Jasmine test suite and Biome linter.