docs(create-vite): list overwrite flag in help

[grzdev]

Summary

• add the supported --overwrite flag to create-vite --help
• add a small CLI test assertion so the help output keeps listing it

Problem

create-vite already parses --overwrite and has behavior coverage for using it with a non-empty target directory, but the flag was missing from the hand-written help output.

That made a supported option harder to discover from create-vite --help.

Fix

• add --overwrite to the help text in packages/create-vite/src/index.ts
• add a CLI test assertion to ensure the help output includes it

Verification

pnpm --filter=./packages/create-vite run build
node packages/create-vite --help
pnpm exec oxfmt --check packages/create-vite/src/index.ts packages/create-vite/__tests__/cli.spec.ts
pnpm exec vitest run packages/create-vite/__tests__/cli.spec.ts
git diff --check -- packages/create-vite/src/index.ts packages/create-vite/__tests__/cli.spec.ts