refactor(app): extract request stage

[james-elicx]

Part 9 of 16 in the staged CDN adapter stack. Depends on #3148.

Summary

• extracts App middleware, routing, and request-context orchestration into a request stage
• dispatches matched work through the App response-stage contract while preserving Pages fallback
• keeps the generated RSC entry thin and preserves navigation, slot, and client-reuse context

Validation

• focused App request-stage, Pages-bridge, worker-entry, and stage-contract tests
• cumulative exact-tip changed-test sweep: 3,461 passed, 2 skipped
• full exact-tip vp check

Review size

• Implementation: +1072 / -49 LOC
• Tests and fixtures: +957 / -15 LOC
• Other (docs, config, lockfile): +3 / -0 LOC
• 24 changed files

Measured against codex/cdn-v2-app-response-stage after rebasing onto main@a6931c0.

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/@vinext/cloudflare@3149

npm i https://pkg.pr.new/create-vinext-app@3149

npm i https://pkg.pr.new/@vinext/types@3149

npm i https://pkg.pr.new/vinext@3149

commit: daa9683

[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 daa9683 against base 29da06e using alternating same-runner rounds. Next.js was unchanged and skipped.

0 improved · 1 regressed · 5 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	2.68 s	2.83 s	🔴 +5.4%
Production build time	vinext	2.90 s	2.89 s	⚫ -0.3%
RSC entry closure size (gzip)	vinext	125.4 KB	125.6 KB	⚫ +0.2%
Server bundle size (gzip)	vinext	216.1 KB	216.4 KB	⚫ +0.1%

View detailed results and traces

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