Nuxt: `sentryUrl`, `--import` guidance, drop import-in-the-middle step

[chargome]

• Module option url → sentryUrl in the AST path and the fallback instructions in src/nuxt/sdk-setup.ts.
• The SDK now emits .output/server/sentry.server.config.mjs for preloading. Update the --import guidance text and docs link.
• v11 instruments via diagnostics channels and no longer registers import-in-the-middle hooks. Remove the iitm install prompt and the Nuxt version-override step. Confirm with the Nuxt SDK owner first.
• Update the nuxt-3 and nuxt-4 e2e tests.

[linear-code]

WIZARD-154