feat: PercentageBarChart

[sverg-cb]

What changed? Why?

PercentageBarChart is a new specialized chart component that renders stacked bar charts where every bar always fills 100% of the value axis. Rather than requiring callers to pre-normalize their data, consumers pass raw non-negative values per segment and the component handles the proportional math internally — each segment's value is divided by the group total and scaled to 100%.

This makes it straightforward to visualize part-to-whole breakdowns (e.g. category share, allocation splits) without any data preprocessing. The value axis is automatically locked to a strict 0–100% scale.

It supports both horizontal (default) and vertical bar orientations, and is built as a thin, focused wrapper around the existing BarChart component — inheriting its rendering, theming, and accessibility foundations while exposing a simpler, opinionated API scoped to the percentage-bar use case.

UI changes

Storybook

Storybook	Light	Dark
Mobile	pbc-mobile-storybk-light.mov	pbc-mobile-storybook-dark.mov
Web	pbc-web-storybk-light.mov	pbc-web-storybook-dark.mov

Docs

Mobile	Web
pbc-docs-mobile.mov	pbc-docs-web.mov

Testing

How has it been tested?

• Unit tests
• Interaction tests
• Pseudo State tests
• Manual - Web
• Manual - Android (Emulator / Device)
• Manual - iOS (Emulator / Device)

Testing instructions

Illustrations/Icons Checklist

Required if this PR changes files under packages/illustrations/** or packages/icons/**

• verified visreg changes with Terran (include link to visreg run/approval)
• all illustration/icons names have been reviewed by Dom and/or Terran

Change management

type=routine
risk=low
impact=sev5

automerge=false

[cb-heimdall]

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