Add orchestrion option in Nuxt

[s1gr1d]

Add a first-class orchestrion option to the @sentry/nuxt module so users can enable diagnostics-channel instrumentation without manually configuring Nitro Rollup plugins.

Findings

• packages/nuxt/src/ currently has no orchestrion references.
• Next.js already exposes this via useDiagnosticsChannelInjection in SentryBuildTimeOptions (packages/nextjs/src/config/types.ts).
• A manual setup exists in the E2E test dev-packages/e2e-tests/test-applications/nuxt-4-orchestrion, which inlines instrumented deps via nitro.externals.inline and adds a Rollup plugin to nitro.rollupConfig.
• @sentry/server-utils provides the orchestrion Rollup plugin at @sentry/server-utils/orchestrion/rollup, but it is not yet a dependency of @sentry/nuxt.

[linear-code]

JS-3076

[sentry-pierre]

I added a short findings section so the next engineer doesn't have to rediscover the Next.js parallel and the E2E test app.