Remove Russian language support and establish no-Russian design principle

docs/07-decisions/adr-036-no-russian-language.md

@@ -0,0 +1,53 @@
+---
+title: 'ADR-036: No Russian Language Support'
+---
+
+# ADR-036: No Russian Language Support
+
+**Status**: Accepted
+
+**Date**: 2026-03-20
+
+## Context
+
+VariScout is a quality analysis tool targeting EU manufacturing and engineering markets. As part of
+product positioning, the team has established a design principle: **VariScout does not support the
+Russian language**.
+
+This is an intentional, deliberate decision — not a gap or oversight. Russian was previously
+scaffolded as part of the broad 33-locale i18n expansion (ADR-025), but inclusion was premature and
+inconsistent with the product's target audience and values.
+
+## Decision
+
+Russian (`ru`) is removed from the supported locale set:
+
+- The `Locale` type union no longer includes `'ru'`
+- `LOCALES` array no longer includes `'ru'`
+- `LOCALE_NAMES` record no longer maps `'ru'`
+- The BCP47 mapping `ru → ru-RU` is removed from the formatting utilities
+- The Russian message catalog (`messages/ru.ts`) is deleted
+
+Russian-speaking users whose browser language is detected as `ru` or `ru-*` will fall back to
+English, following the standard `detectLocale()` fallback chain.
+
+## Design Principle
+
+> **VariScout does not support the Russian language.**
+
+This applies to:
+- UI localization (message catalogs, translated strings)
+- Browser language auto-detection
+- Number/date formatting via `Intl` APIs
+- AI response locale hints (CoScout will not be instructed to respond in Russian)
+- Any future language selector UI
+
+This principle does **not** affect Ukrainian (`uk`), which remains a fully supported locale.
+
+## Consequences
+
+- 32 supported locales (down from 33)
+- Russian-browser users see English UI
+- Removes ~5 KB lazy-loaded chunk from the production bundle
+- Maintains type safety — TypeScript enforces the exhaustive `Record<Locale, string>` pattern,
+  so all locale maps stay consistent after removal

packages/core/src/i18n/format.ts

@@ -22,7 +22,6 @@ const BCP47: Record<Locale, string> = {
   it: 'it-IT',
   nl: 'nl-NL',
   pl: 'pl-PL',
-  ru: 'ru-RU',
   tr: 'tr-TR',
   sv: 'sv-SE',
   da: 'da-DK',