[Audit] useLocale - ensure parity with Vuetify createLocale

[johnleider]

Summary

Ensure useLocale has feature parity with Vuetify 3's createLocale.

Research Findings

v0 Architecture

• Adapter Pattern: LocaleAdapter interface with pluggable implementations
• Trinity Pattern: Full support via createLocaleContext()
• RTL Support: Built-in RTL detection and handling
• Message Interpolation: Template string interpolation for dynamic content

Current Status

v0's useLocale is largely feature-complete with Vuetify 3. Both provide:

• Locale switching
• Message retrieval with interpolation
• RTL detection
• Reactive locale state

Minor Alignment Items

Aspect	v0	Vuetify 3	Action
API naming	useLocale()	useLocale()	✅ Aligned
RTL property	✅	✅	✅ Aligned
Message format	Template interpolation	Template interpolation	✅ Aligned
Adapter pattern	✅ Pluggable	❌ Built-in only	v0 advantage

Tasks

• Verify message interpolation syntax matches Vuetify 3
• Ensure RTL detection logic is equivalent
• Document any API differences
• Test with Vuetify 3 locale message files

Files

• v0: packages/0/src/composables/useLocale/index.ts
• v0 adapter: packages/0/src/composables/useLocale/adapters/
• Vuetify 3: packages/vuetify/src/composables/locale.ts

[johnleider]

Updated Analysis (Mar 11)

v0's useLocale is largely at parity with Vuetify's createLocale. Both have locale switching, message interpolation, RTL detection, and reactive state. v0 has the advantage of a pluggable adapter pattern.

Remaining integration work (tracked in #114):

• Provide locale to useDate for locale-aware formatting
• Persist locale preference via useStorage
• RTL detection for useTheme CSS variable injection

No additional gaps found.

[johnleider]

Final analysis complete before implementation phase. All base level features properly supported.