refactor(app): extract response-stage renderer

[james-elicx]

Part 8 of 16 in the staged CDN adapter stack. Depends on #3147.

Summary

• extracts App page and route-handler rendering into the App response stage
• preserves RSC and HTML streaming, middleware context, headers, redirects, not-found handling, and response finalization
• keeps route-handler runtime loading lazy and generated entries focused on wiring

Validation

• focused App route-handler and RSC-handler tests
• cumulative exact-tip changed-test sweep: 3,461 passed, 2 skipped
• full exact-tip vp check

Review size

• Implementation: +1174 / -103 LOC
• Tests and fixtures: +1542 / -126 LOC
• Other (docs, config, lockfile): +4 / -0 LOC
• 15 changed files

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

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/@vinext/cloudflare@3148

npm i https://pkg.pr.new/create-vinext-app@3148

npm i https://pkg.pr.new/@vinext/types@3148

npm i https://pkg.pr.new/vinext@3148

commit: 29da06e

[github-actions]

Performance benchmarks

Compared 29da06e against base 14d0de0 using alternating same-runner rounds. Next.js was unchanged and skipped.

0 improved · 2 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	3.11 s	3.09 s	⚫ -0.8%
Production build time	vinext	3.40 s	3.42 s	⚫ +0.7%
RSC entry closure size (gzip)	vinext	119.8 KB	125.3 KB	🔴 +4.6%
Server bundle size (gzip)	vinext	203.4 KB	216.1 KB	🔴 +6.2%

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
workers-cache	preview	production
static-export	preview	production
web	preview	production