feat(workflow-operator): volcano plot labels follow columns - #9040

What changes were proposed in this PR?

Root cause: VolcanoPlotOpDesc.generatePythonCode hard-codes the y column as the literal "-log10(pvalue)" and plots it under that name, so the y axis always says -log10(pvalue) even when the selected column is padj. The title is the literal "Volcano Plot" and the x axis and color bar show the raw effect column name. None of this can be changed from the property panel.

Before:  P-Value Column = padj  ->  y column "-log10(pvalue)"  ->  y axis "-log10(pvalue)"
After:   P-Value Column = padj  ->  y column "-log10(padj)"    ->  y axis "-log10(padj)", or the Y Label the user typed

The y column is now named after the selected p-value column, so the axis and the hover text say which column was transformed. Three optional label properties are added, empty by default:

The color bar has no label of its own: the points are colored by the effect column, the same column that is on the x axis, so the color bar carries the X Label text (or the effect column name when X Label is empty). If a later change lets the color encode a different column, a label for it would come with that change.

The labels go through fig.update_layout(xaxis_title, yaxis_title, coloraxis_colorbar_title_text), same as Line Chart's X Label / Y Label. Each label is an EncodableString, so quotes and non-ASCII text are fine. A whitespace-only field counts as empty. The hover box still shows raw column names (plotly behaviour, same as Line Chart).

Behavior change for saved workflows: a workflow with padj as the p-value column now renders -log10(padj) instead of -log10(pvalue). That is the fix.

Since #8504 merged, the operator also has an export path, generateStandaloneCode(), which writes the same figure as a standalone script. It carried the same hard-coded "-log10(pvalue)" and title="Volcano Plot", so this PR applies the same change there: the y column is named after the selected p-value column and the three labels go through fig.update_layout as escaped Python literals (the export has no decoder, so pyStringLiteral escapes quotes and backslashes). The engine template and the exported script now label the figure the same way.

Rebase note: coloraxis_colorbar_title_text is emitted unconditionally, in both templates. Once the PR for the significance coloring (#9039) lands, the categorical mode has no coloraxis, so whichever branch rebases second needs to make that entry conditional.

Figures below are the operator's generated Python from main and from this branch, run on the 430-gene example workflow from the issue; the third one has the title and both axis labels filled in.

Before	After (defaults)	After (labels set)

Any related issues, documentation, discussions?

Closes #9037

PR #8504 (merged) added the generateStandaloneCode() export path with the same hard-coded "-log10(pvalue)"; the mirroring described above is the follow-up it needed.

How was this PR tested?

New tests in VolcanoPlotOpDescSpec, written before the source change:

• y column and axis are named after the selected p-value column; the old literal is gone
• every label falls back to its default when empty or whitespace-only
• a set label replaces its default and reaches the code only as a decode site (sentinels with quotes, backslash, non-ASCII)
• the color bar title follows X Label when it is set and the effect column name otherwise
• one set label leaves the other two at their defaults
• a workflow JSON saved before this change (only the two column keys) generates byte-for-byte the same code as a default-constructed operator
• generateStandaloneCode: the y column and axis are named after the p-value column (including a name with a quote, p"adj), the labels fall back to the column-derived defaults, a set label is emitted as an escaped literal and the default title is gone, the color bar carries the X Label text, and whitespace-only keeps the default

sbt -Dsbt.server.forcestart=true "WorkflowOperator/testOnly *VolcanoPlotOpDescSpec"
# Tests: succeeded 15, failed 0, canceled 0, ignored 0, pending 1   (the pending one is pre-existing)

sbt -Dsbt.server.forcestart=true "WorkflowOperator/scalafmtAll" "WorkflowOperator/Test/scalafmtAll"
sbt -Dsbt.server.forcestart=true "WorkflowOperator/scalafixAll --check"
# success

Smoke run: the generated code was executed outside Texera (pytexera stubbed, pandas + plotly 5.24.1) on the 430-gene mock table. Defaults give title Volcano Plot, x lfc_shrunk, y -log10(padj), color bar lfc_shrunk; with the labels set the figure shows the typed text; whitespace-only title and y label fall back to the defaults. The exported script for the default and the all-labels configuration parses with ast.parse.

Was this PR authored or co-authored using generative AI tooling?

Yes. Generated-by: Claude Code (claude-fable-5-1). Co-authored with Claude; the author reviewed the change before submission.