feat(tracing): add App fetch spans

[james-elicx]

Summary

• emit Next.js-compatible AppRender.fetch spans through the shared framework tracer
• record HTTP and fetch cache outcome attributes while honoring NEXT_OTEL_FETCH_DISABLED and internal fetches
• prove real @sentry/nextjs parentage and attributes on Cloudflare Workerd

Next.js parity

Pinned against vercel/next.js@b421cadefd31c1b59d117842021ded7c1ebaf5b4, especially:

• packages/next/src/server/lib/patch-fetch.ts
• packages/next/src/server/lib/patch-fetch.test.ts
• test/e2e/opentelemetry/instrumentation/opentelemetry.test.ts

No OpenTelemetry package is added as a required vinext dependency, and no Sentry-specific runtime path is introduced.

Validation

• vp check
• vp test run tests/app-fetch-tracing.test.ts tests/fetch-cache.test.ts tests/framework-tracer.test.ts tests/workers-tracing.test.ts (178 passed)
• vp run vinext#build
• PLAYWRIGHT_PROJECT=cloudflare-sentry-app pnpm exec playwright test (15 passed)
• independent correctness review: clean
• independent Next.js parity review: clean

Stack parent: #3266

[pkg-pr-new]

Open in StackBlitz

@vinext/cloudflare

npm i https://pkg.pr.new/cloudflare/vinext/@vinext/cloudflare@3267

create-vinext-app

npm i https://pkg.pr.new/cloudflare/vinext/create-vinext-app@3267

@vinext/types

npm i https://pkg.pr.new/cloudflare/vinext/@vinext/types@3267

vinext

npm i https://pkg.pr.new/cloudflare/vinext@3267

@cloudflare/workers-response-store

npm i https://pkg.pr.new/cloudflare/vinext/@cloudflare/workers-response-store@3267

commit: 0bead68

[github-actions]

Performance benchmarks

Compared 0bead68 against base be5c13b using alternating same-runner rounds. Next.js was unchanged and skipped.

0 improved · 0 regressed · 6 within ±1.5%

Scenario	Framework	Baseline	Current	Change
Client bundle size (gzip)	vinext	142.3 KB	142.3 KB	⚫ -0.0%
Client entry size (gzip)	vinext	129.6 KB	129.6 KB	⚫ -0.0%
Dev server cold start	vinext	3.31 s	3.28 s	⚫ -0.9%
Production build time	vinext	3.85 s	3.82 s	⚫ -0.8%
RSC entry closure size (gzip)	vinext	123.9 KB	124.3 KB	⚫ +0.3%
Server bundle size (gzip)	vinext	214.5 KB	214.8 KB	⚫ +0.2%

View detailed results and traces

_{🟢 improvement · 🔴 regression · ⚫ change below 1.5% · paired base/head}

[github-actions]

Example	Preview	Production	Original
app-router-cloudflare	preview	production
pages-router-cloudflare	preview	production
app-router-playground	preview	production	original
realworld-api-rest	preview	production
nextra-docs-template	preview	production
benchmarks	preview	production
hackernews	preview	production	original
response-store-demo	preview	production
static-export	preview	production
web	preview	production