fix(engine): editorial defaults audit

[rileyhilliard]

Summary

Audited all rendering defaults against the 12-item editorial design checklist (plan 04). 9 items passed, 3 fixed:

• Tabular figures on all numeric text: added font-variant-numeric: tabular-nums to endpoint label values, bar/column/pie/dot data labels, and barlist value labels. Axis ticks, metrics, tooltips, and table cells already had it.
• X domain line hidden for non-grounded marks: line, area, scatter, and dot charts no longer render the x-axis baseline. Bar/tick/lollipop keep it. User-explicit axis.domain always wins.
• Scatter vertical gridlines: scatter charts now show x-axis gridlines by default (editorial convention for two-quantitative-axis charts). User axis.grid overrides.

Test plan

• All 2467 tests pass
• Lint, typecheck, build green
• 8 visual baselines regenerated (line/area charts lost their x domain line)
• 20/20 visual regression tests pass
• Code review: moved GROUNDED_MARKS to module scope, added missing dot chart tabular-nums

https://claude.ai/code/session_01S8jmshMshTq7Gs2RYKsd5w

Summary by CodeRabbit

• Bug Fixes
  • Improved x-axis defaults so baseline and gridlines now appear more consistently based on chart type.
  • Fixed axis baseline behavior in rendering tests to match grounded vs. non-grounded charts.
  • Made numeric labels align more evenly across bars, columns, dots, pies, and endpoint labels.
  • Updated axis property expectations so default settings are handled more accurately.

[coderabbitai]

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ℹ️ Recent review info

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Review profile: CHILL

Plan: Pro

Run ID: 3ebe5b51-9733-4348-a23d-edafc60b15e1

📥 Commits

Reviewing files that changed from the base of the PR and between d23251d and 3d47038.

⛔ Files ignored due to path filters (9)

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• e2e/visual/__screenshots__/stories.spec.ts-snapshots/compact-line-320px-visual-darwin.png is excluded by !**/*.png
• e2e/visual/__screenshots__/stories.spec.ts-snapshots/dark-mode-line-visual-darwin.png is excluded by !**/*.png
• e2e/visual/__screenshots__/stories.spec.ts-snapshots/legend-bottom-right-visual-darwin.png is excluded by !**/*.png
• e2e/visual/__screenshots__/stories.spec.ts-snapshots/legend-top-visual-darwin.png is excluded by !**/*.png
• e2e/visual/__screenshots__/stories.spec.ts-snapshots/line-multi-series-visual-darwin.png is excluded by !**/*.png
• e2e/visual/__screenshots__/stories.spec.ts-snapshots/multi-series-area-overlap-visual-darwin.png is excluded by !**/*.png
• e2e/visual/__screenshots__/stories.spec.ts-snapshots/multi-series-area-stacked-visual-darwin.png is excluded by !**/*.png
• packages/engine/src/__tests__/__snapshots__/compile-snapshot.test.ts.snap is excluded by !**/*.snap

📒 Files selected for processing (9)

• packages/engine/src/__tests__/axes.test.ts
• packages/engine/src/barlist/compile-barlist.ts
• packages/engine/src/charts/bar/labels.ts
• packages/engine/src/charts/column/labels.ts
• packages/engine/src/charts/dot/labels.ts
• packages/engine/src/charts/pie/labels.ts
• packages/engine/src/endpoint-labels/compute.ts
• packages/engine/src/layout/axes.ts
• packages/vanilla/src/__tests__/svg-renderer.test.ts

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📝 Walkthrough

Walkthrough

This PR adds fontVariant: 'tabular-nums' to numeric label styles across bar list, bar, column, dot, pie, and endpoint-label renderers for consistent glyph alignment. It also updates x-axis default logic to conditionally set domainLine and gridlines based on markType, introducing a GROUNDED_MARKS set, with corresponding test updates.

Changes

Tabular Numerals and Mark-Aware Axis Defaults

Layer / File(s)	Summary
Tabular-nums font variant for numeric labels packages/engine/src/barlist/compile-barlist.ts, packages/engine/src/charts/bar/labels.ts, packages/engine/src/charts/column/labels.ts, packages/engine/src/charts/dot/labels.ts, packages/engine/src/charts/pie/labels.ts, packages/engine/src/endpoint-labels/compute.ts	Adds fontVariant: 'tabular-nums' to numeric label styles across bar list, bar, column, dot, pie, and endpoint-label value rendering.
Mark-aware x-axis domainLine/gridline defaults packages/engine/src/layout/axes.ts, packages/engine/src/__tests__/axes.test.ts, packages/vanilla/src/__tests__/svg-renderer.test.ts	Introduces GROUNDED_MARKS (bar, tick, lollipop) to compute x-axis domainLine defaults, changes gridlines default to enable for point marks, and updates unit/integration tests to reflect grounded vs. non-grounded baseline behavior.

Estimated code review effort: 2 (Simple) | ~12 minutes

Possibly related PRs

• tryopendata/openchart#64: Both PRs modify the same computeAxes logic in packages/engine/src/layout/axes.ts affecting x/y axis defaults and gridline/tick handling, with related test updates.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title matches the PR’s main theme: auditing and fixing editorial defaults in the engine.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

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• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch worktree-editorial-defaults-audit

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