Custom PNG save button fails to capture the full plot

[Ttheegela]

Describe the bug
The custom Save PNG button did not reliably capture the full plot. In Bokeh 3.8.1 the Bokeh.index object is not exposed on the global Bokeh object, so all Bokeh.index.find_one calls silently failed, resulting in an empty or blank PNG.

Root cause
The canvas_helper approach relied on intercepting Bokeh.embed.embed_items to capture view objects. This is not a stable Bokeh API and broke in Bokeh 3.8.1.

Resolution
Custom PNG save button removed entirely. The Bokeh toolbar download button (top-right of each plot) is the supported and reliable method for saving plots.

Resolved in
Commit d3a08d1

[Ttheegela]

Resolved in commit d3a08d1 the custom PNG save button was removed. Bokeh 3.8.1 renders legends as HTML overlays (not on the canvas), which made reliable full-plot capture impossible. The toolbar save button (top-right of each plot) captures the full plot correctly and should be used instead.