fix(Switch): persistently mount busy live region and localize loading announcement (#6114)

[Geervan]

Fixes #6114.

Previously, Switch rendered its busy announcement live region dynamically only while isBusy was true ({isBusy && <VisuallyHidden role="status">Loading</VisuallyHidden>}). This caused two defects:

1. Born with content: The live region was mounted at the same moment its text appeared. Because screen readers observe text mutations within pre-existing live regions rather than newly inserted nodes with existing content, the loading announcement was typically silent.
2. Hardcoded English: The string "Loading" was hardcoded in English instead of going through the useTranslator i18n system.

This PR aligns Switch with the persistent live-region pattern used by Button:

• Unconditionally renders <VisuallyHidden role="status" aria-live="polite"> so the container is always mounted.
• Sets its text to empty string "" when idle and dynamically updates it to t('@astryx.switch.loading') when isBusy is true.
• Adds the @astryx.switch.loading key to packages/core/locales/en.json.

Changes

• packages/core/src/Switch/Switch.tsx: Hooked useTranslator and converted the live region to be persistently mounted with dynamic translated text.
• packages/core/locales/en.json: Added @astryx.switch.loading translation entry.
• packages/core/src/Switch/Switch.test.tsx: Added regression unit tests for:
  • Empty persistent live region present when idle.
  • Live region updating to "Loading" when isLoading is enabled.
  • Localization of the loading announcement through InternationalizationProvider overrides.
  • Live region announcing "Loading" during async changeAction transitions and clearing on resolution.
• .changeset/switch-busy-announcement.md: Added changeset entry for patch release.

Verification

• npx vitest run packages/core/src/Switch/Switch.test.tsx (58/58 passed)
• node scripts/check-i18n-catalog.mjs (passed with 0 errors)
• npx vitest run packages/core/src/Button/Button.test.tsx packages/core/src/i18n/useTranslator.test.tsx (52/52 passed)
• node scripts/check-changesets.mjs (passed)

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Project	Deployment	Actions	Updated
astryx	Ready	Preview	Sep 8, 2026 11:19am UTC

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Modified Components

Switch _{(@astryxdesign/core)} · View in Storybook

Metric	Before	After	Delta
Bundle Size (ESM)	N/A	N/A	N/A
Lines of Code	N/A	497	-
Complexity	N/A	Very High (46)	-

Bundle Size Summary

Package	Size (ESM)	Size (CJS)	Gzipped
@astryxdesign/core	N/A	4.8KB	1.2KB

Accessibility Audit

Status: No accessibility violations detected.

Visual Regression

Status: No visual change across 2 compared shot(s).

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[cixzhang]

Thanks for this fix! This is very close. We'll likely want to use the useAnnounce pattern here over visually hidden.

[cixzhang]

We likely want to be using useAnnounce instead of VisuallyHidden which is the older pattern. The useAnnounce hook will include a stable live region and bypass the issue without introducing a permanent DOM element per switch.

[Geervan]

Updated to use the useAnnounce hook instead of VisuallyHidden as suggested!

Announcements now route through the shared singleton live region without introducing per-switch DOM nodes, let me know if I still missed any corners