docs(cli): document vuetify add registry and local library lifecycle

[johnleider]

Summary

Documents the official docs registry consumer on the Vuetify CLI guide (/guide/tooling/vuetify-cli):

• vuetify add <feature> — seed components/composables/plugins from 0.vuetifyjs.com/registry
• Plugin install-first path (use-theme, etc.)
• vuetify.json tracking via list / status
• generate, diff, refresh, registry build
• Multi-registry aliases and custom origins

Pairs with:

• Seed: docs: publish a static registry for vuetify add #721 (merged, live)
• CLI consumer: feat(add): write v0 examples into a project from the registry cli#27

Test plan

• Preview /guide/tooling/vuetify-cli — Commands table and ### add sections render
• Links to useTheme / MCP / registry index resolve
• Note about CLI version vs live seed is accurate relative to docs(use-registry): update page content #27 ship status

[johnleider]

Local walkthrough against live registry + this guide

Used CLI from main post-#27 (@vuetify/cli dist) and https://0.vuetifyjs.com/registry.

Docs step	Result
add dialog --yes	✅ wrote + tracked; styling preflight warned for missing useTheme then mapped uno colors
list / status	✅
add use-theme --yes	✅ plugin file + registerPlugins wire
add use-locale --yes	✅
add create-data-table --example features	✅ multi-file
add data-table --example gallery	❌ invalid — fixed in follow-up commit to use real registry ids
generate MyCard / generate --dir …	✅; --dir was clobbering alias (CLI fix: vuetifyjs/cli fix/generate-dir-alias)
diff / refresh	✅ after alias fix
registry build + host parent + --registry / @local/…	✅

Ready to merge once the example fix is on the branch.