fix(cloudflare): keep CDN warmup correct with custom adapters and i18n

[james-elicx]

Summary

Keeps deploy-time CDN warming correct when applications use custom cache adapters or hybrid App/Pages Router i18n routes.

• expose build-identity response headers as a generic CDN adapter capability; the built-in Cloudflare adapter now guarantees X-Vinext-Build-Id on every page response
• verify staged HTML only when the adapter declares that capability; strict warmup fails before upload when exact-build HTML warming cannot be proven, while non-strict deploys defer that HTML work until after promotion and label it best-effort
• validate response build identity before accepting cache admission or a non-cacheable skip, so an old deployment's BYPASS response cannot suppress warming for a route that became cacheable
• treat Cloudflare cache admission statuses as authoritative while rejecting unsafe plain Set-Cookie MISS responses and accepting explicit field-qualified cookie policy
• preserve hybrid route ownership under Pages Router i18n by normalizing locale prefixes for page matching without reclassifying locale-prefixed App routes as Pages API routes

This is stacked on #3023.

Validation

• 88 focused tests across CDN response validation, staged deploy orchestration, adapter capabilities, prerender path discovery, deploy config wiring, and hybrid i18n handoff
• targeted formatting, lint, and type checks for all 11 changed files
• vp run vinext#build
• vp run @vinext/cloudflare#build

Cloudflare admission behavior was checked against the current cache response and CDN-Cache-Control documentation. The hybrid locale/API behavior follows Next.js' test/e2e/i18n-api-support/index.test.ts coverage.

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/@vinext/cloudflare@3024

npm i https://pkg.pr.new/create-vinext-app@3024

npm i https://pkg.pr.new/@vinext/types@3024

npm i https://pkg.pr.new/vinext@3024

commit: c36af17

[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
workers-cache	preview	production
web	preview	production

[github-actions]

Performance benchmarks

Compared c36af17 against base 4035031 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	142.0 KB	142.0 KB	⚫ -0.0%
Client entry size (gzip)	vinext	129.3 KB	129.3 KB	⚫ -0.0%
Dev server cold start	vinext	2.58 s	2.59 s	⚫ +0.4%
Production build time	vinext	2.80 s	2.79 s	⚫ -0.3%
RSC entry closure size (gzip)	vinext	116.0 KB	116.0 KB	⚫ -0.0%
Server bundle size (gzip)	vinext	197.5 KB	197.5 KB	⚫ -0.0%

View detailed results and traces

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

[james-elicx]

Superseded by consolidated PR #3040. No commits were dropped or rewritten: #3040 now contains this exact linear commit as part of #3021–#3040. Closing only the redundant draft PR.