fix(cache): preserve prerender metadata across completion races

[james-elicx]

Capability stack 1/9. Exact head: 1fd53d7b899a4e34cb0dbf49b99168936a942b6a. Base: main.

Full chain: #3108 → #3090 → #3091 → #3092 → #3103 → #3093 → #3094 → #3098 → #3113.

Summary

This keeps two independent completion-ordering fixes outside the cacheability implementation layers:

• drain the single-chunk stream-test transform before releasing its reader, preventing Node 24.20 cancellation from racing asynchronous flush()
• preserve prerender cache-life metadata when the HTML navigation footer finalizes before the outer render lifecycle consumes that metadata
• add a deterministic regression for the prerender ordering

Without the stale-time fix, prerendered HTML can omit staleTimeSeconds even though the prerender manifest records the correct value.

No staged probing, cacheability manifest, CDN-admission behavior, or warming behavior is introduced here. #3090 begins the capability itself.

Review size

Layer-only diff against this PR's base: 3 files, +83/-8.

Validation

• layer exact-head CI is green
• prior cumulative focused validation through feat(cache): probe Pages Router cacheability #3098 — 2,024/2,024
• current full-stack cumulative changed-file suites — 2,864/2,864
• current full-stack PPR probe/admission/Pages built-workerd E2E — 8/8
• current full-stack vp check and git diff --check

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/@vinext/cloudflare@3108

npm i https://pkg.pr.new/create-vinext-app@3108

npm i https://pkg.pr.new/@vinext/types@3108

npm i https://pkg.pr.new/vinext@3108

commit: 1fd53d7

[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 1fd53d7 against base c1a78a7 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	142.2 KB	142.2 KB	⚫ -0.0%
Client entry size (gzip)	vinext	129.5 KB	129.5 KB	⚫ -0.0%
Dev server cold start	vinext	3.14 s	3.13 s	⚫ -0.4%
Production build time	vinext	3.56 s	3.54 s	⚫ -0.6%
RSC entry closure size (gzip)	vinext	116.6 KB	116.6 KB	⚫ 0.0%
Server bundle size (gzip)	vinext	198.1 KB	198.1 KB	⚫ -0.0%

View detailed results and traces

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