Feat tooltip stacked area chart

[jacobvjk]

Summary

To make the overall experience of benchmark charts more consistent across plot types, this PR:

• adds a hover tooltip to NormalizedStackedAreaChart showing all technology shares for the nearest year, with a vertical guideline marking it
• ensures the tooltip sits beside the added vertical guideline and auto-flips/repositions to stay within the chart bounds
• slightly enlarges the comparison view's 3-pathway chart size to give the tooltip more room

Related issues

Closes: #908

This is also a preparation for #904

Testing

Manually tested the plot behavior, none of the plot components currently have dedicated tests

Checklist

• PR is focused on a single concern
• Tests pass locally and in CI
• Docs updated for user-visible changes
• AI-assisted portions declared (see CONTRIBUTING.md)

[github-actions]

Expected version change and release notes:

1.16.0-dev.15 (v1.16.0-dev.14...feat-tooltip-stacked-area-chart ) (2026-08-19T07:22 UTC)

Features

• add tooltip to NormalizedStackedAreaChart (ee13009)

[github-actions]

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[Copilot]

Pull request overview

This PR improves interaction consistency across benchmark plot types by adding an x-axis-driven hover tooltip to NormalizedStackedAreaChart, including a vertical guideline and tooltip positioning logic to stay within bounds. It also increases the 3-pathway comparison chart dimensions to give the new tooltip more room.

Changes:

• Add pointer-driven tooltip + vertical guideline to NormalizedStackedAreaChart, showing nearest-year shares for all technologies.
• Implement tooltip auto-flip/reposition logic to keep the tooltip within the chart area while keeping the guideline visible.
• Increase the 3-pathway comparison panel dimensions to reduce tooltip crowding.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/components/NormalizedStackedAreaChart.tsx	Adds guideline + hover tooltip that lists all technology shares for the nearest year and repositions to avoid clipping.
src/components/ComparisonPlots.tsx	Enlarges 3-pathway comparison chart dimensions to provide more space for the new tooltip.

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[github-actions]

Azure Static Web Apps: Your stage site is ready! Visit it here: https://proud-glacier-0f640931e-909.westus2.2.azurestaticapps.net

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated no new comments.