fix(i18n): localize Timestamp relative formats

[nynexman4464]

Problem

Timestamp's absolute formats follow InternationalizationProvider, but relative, relative_short, and the relative branch of auto still assemble English phrases manually. A French provider therefore renders 2 hours ago, now, and yesterday in English.

Change

• Preserve Timestamp's existing second/minute/hour/day/month/year thresholds and future-clock-skew handling.
• Format the selected value and unit with the provider locale through Intl.RelativeTimeFormat.
• Use the native long style for relative/auto and narrow for relative_short.
• Keep long-form now and yesterday idioms, while compact output stays numeric.
• Cache formatters by locale, style, and numeric mode.
• Add the pure formatter to the strict raw-Intl infrastructure boundary.

Native formatting also replaces the English-only in a few seconds special case with the locale's exact seconds form, such as in 31 seconds.

Intl.RelativeTimeFormat formats a signed quantity and unit; it has no calendar option and does not convert or inspect calendar dates. Gregorian enforcement therefore does not apply here. The raw-Intl lint did catch direct construction in Timestamp.tsx; construction now lives in a narrowly approved pure helper that requires the provider locale.

Visual evidence

The permanent English Storybook story covers every past and future transition point. French below is a temporary provider override used only for evidence.

Before — French provider ignored

After — English

After — French

Fixes #5074.

Test plan

• Regression proof against the old implementation: three new provider-locale cases failed with English output (2 hours ago, 2h ago, and now) where French was expected.
• pnpm exec vitest run --project ui packages/core/src/Timestamp/Timestamp.test.tsx — 92 passed.
• pnpm exec vitest run --project node internal/eslint-plugin-astryx/no-raw-intl-locale.test.mjs — 100 passed.
• Permanent Storybook story: English past/future transition points at present, seconds, minutes, hours, days, months, and years.
• pnpm rtl:audit --filter Timestamp — verified N/A with 0 coverage gaps; Timestamp has no directional visual or behavior.
• pnpm lint:strict — passed with existing warnings only.
• pnpm -F @astryxdesign/core build — passed.

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Project	Deployment	Actions	Updated
astryx	Ready	Preview	Sep 2, 2026 8:16pm UTC

[github-actions]

PR Analysis Report

Preview availability: Storybook and Sandbox were not published for this CI run.

Modified Components

Timestamp _{(@astryxdesign/core)}

Metric	Before	After	Delta
Bundle Size (ESM)	N/A	N/A	N/A
Lines of Code	N/A	643	-
Complexity	N/A	Very High (44)	-

Bundle Size Summary

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

Accessibility Audit

Status: 1 accessibility violation(s) found — 1 serious.

Timestamp - 1 issue(s)

• 🟠 serious: Ensure the contrast between foreground and background colors meets WCAG 2 AA minimum contrast ratio thresholds
  • Rule: color-contrast · Affects 1/20 stories · Learn more
  • WCAG: 1.4.3 (Level AA)

Visual Regression

12 added · 0 removed. View the report

A repository maintainer can accept these exact frames: /accept-visual 33568304679/1 <why every changed frame is correct>

Added — After

Added — After

Added — After

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_{Generated by PR Enrichment workflow | View full report}

[cixzhang]

Thanks this is good. The provider-locale regression is fixed across relative, compact, and auto modes. Please resolve the generated RTL-audit list conflict before merge.

[Reviewed by Robohands]

[nynexman4464]

/accept-visual 33568304679/1 screens look good, test is essentially plain default text

[github-actions]

Visual changes accepted for 4257c1b81d6a. A new push invalidates this approval; after merge, the reviewed AFTER frames must reproduce before the baseline is promoted.

[cixzhang]

Thanks, this is good. Non-English providers now get native relative timestamps across relative, compact, and auto modes, and the merge resolves the RTL-audit conflict.

[Reviewed by Robohands]