feat(build): define adapter-owned worker stages

[james-elicx]

Part 2 of 16 in the staged CDN adapter stack. Depends on #3082.

Summary

• defines transport-neutral request and response stage contracts in core vinext
• keeps platform transport and stage interaction generic for RPC, service-binding, or HTTP adapters
• intentionally publishes only the neutral type contract; build selection and lazy loader exports arrive atomically in feat(build): select adapter-owned worker stages #3150

Validation

• vp test run tests/cache-adapters-config.test.ts
• focused format, lint, and type checks
• cumulative exact-tip changed-test sweep: 3,461 passed, 2 skipped

Review size

• Implementation: +109 / -2 LOC
• Tests and fixtures: +0 / -0 LOC
• Other (docs, config, lockfile): +4 / -0 LOC
• 3 changed files

Measured against codex/cdn-stack-tooling after rebasing onto main@a6931c0.

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/@vinext/cloudflare@3142

npm i https://pkg.pr.new/create-vinext-app@3142

npm i https://pkg.pr.new/@vinext/types@3142

npm i https://pkg.pr.new/vinext@3142

commit: b614b12

[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
static-export	preview	production
web	preview	production

[github-actions]

Performance benchmarks

Compared b614b12 against base 5713241 using alternating same-runner rounds. Next.js was unchanged and skipped.

2 improved · 0 regressed · 4 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	3.26 s	3.18 s	🟢 -2.5%
Production build time	vinext	3.79 s	3.68 s	🟢 -2.9%
RSC entry closure size (gzip)	vinext	119.2 KB	119.2 KB	⚫ +0.0%
Server bundle size (gzip)	vinext	202.8 KB	202.8 KB	⚫ +0.0%

View detailed results and traces

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