[Integration] Convert Vuetify to use @vuetify/0 useTheme

[johnleider]

Summary

Convert Vuetify 3 to use @vuetify/v0 useTheme.

Research Findings

Breaking Changes Required

1. Remove monolithic style generation - Delegate to adapter
2. Remove hardcoded DOM access - Use adapter interface
3. Replace color utilities - Use adapter for genOnColors(), genVariations()
4. Remove system theme logic - Add as adapter feature or separate composable
5. API change: change(name) → select(id)
6. Remove makeThemeProps() - v0 uses composition, not props
7. Class calculation: v3 class="v-theme--${name}" → v0 data-theme="${id}"
8. Options restructure: v0 { default, themes, palette } vs v3 { defaultTheme, themes, variations }

Recommended Approach

Create Vuetify3ThemeAdapter that provides:

• genOnColors() for auto foreground colors
• genVariations() for lighten/darken
• System theme detection
• Utility CSS class generation
• CSS layers support
• Scoping support

Migration Path

1. v0 adds missing features (see [Audit] useTheme - ensure parity with Vuetify createTheme #103)
2. Create Vuetify3ThemeAdapter extending ThemeAdapter
3. Vuetify 3 uses v0 with custom adapter
4. Gradual migration of component theme props

Dependencies

• [Audit] useTheme - ensure parity with Vuetify createTheme #103 - Audit useTheme parity

[johnleider]

vuetifyjs/vuetify#22765