docs(option): document missing option properties

[Justin-ZS]

Summary

• document toolbox.backgroundColor in English and Chinese option docs
• expand dataZoom-slider.textStyle docs to include supported text box styles while keeping unsupported align, verticalAlign, and rich hidden
• document recursive children for series-tree.data items
• document additional confirmed missing option docs: datasetId, grid.opacity, series.tooltip.show, series.tooltip.trigger, series.data.tooltip.show, series-bar.encode.label, series-pie.encode.itemName, series-heatmap.dimensions, series-graph.links.tooltip, series-sankey.links.tooltip, series-sankey.data.label.formatter, series-custom.renderItem.return_text.style.rich, and series-pie.label.silent
• correct the generated default for series-pie.label.show to true

Not included

• option.textStyle.backgroundColor: not documented because GlobalTextStyleOption in ECharts source does not support backgroundColor
• dataZoom-slider.dataBackgroundColor: not documented because it is a deprecated legacy option; borderColor is the current documented option
• series-pie.label.textStyle: not documented because textStyle under label is a deprecated compatibility hierarchy that is flattened by the preprocessor; current docs already document the flattened label style properties
• series-custom.label: not documented because it is marked @deprecated in CustomSeriesOption
• series-candlestick.markArea.label.formatter and series-scatter.markArea.data.0.label.formatter: not changed because both are already generated in the option schema
• The calendar heatmap encode behavior mentioned in [Bug] 'encode' fails in heatmap series with calendar coordinate system. dimensions works instead echarts#20748 is a runtime issue and is not addressed here; this PR only documents the supported series-heatmap.dimensions option

Verification

• npm run build
• git diff --check
• source-schema checks for en/zh option docs confirmed the newly documented paths are generated, including grid.opacity, series.datasetId, series.tooltip.trigger, series.data.tooltip.show, series-bar.encode.label, series-pie.encode.itemName, series-heatmap.dimensions, series-graph.links.tooltip.show, series-sankey.links.tooltip.show, series-sankey.data.label.formatter, series-custom.renderItem.return_text.style.rich, series-pie.label.silent, and series-pie.label.show with default true

Fixes apache/echarts#21643