fix(cloudflare): preserve strict CDN warmup invariants

[james-elicx]

Summary

• abort strict warmup before promotion when the current traffic split cannot stage the upload at 0%
• fail no-promote mode when staged readiness fails instead of returning an unwarmed 0% version as success
• apply the configured warmup retry budget to readiness failures while retaining the fixed six-probe stability window

Scope

This is a focused follow-up from the cumulative RSC prewarming review. It changes only staged deploy failure semantics and focused tests.

Validation

• 78 focused Cloudflare warm/deploy/version tests passed
• vp check passed
• @vinext/cloudflare build passed

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/@vinext/cloudflare@3039

npm i https://pkg.pr.new/create-vinext-app@3039

npm i https://pkg.pr.new/@vinext/types@3039

npm i https://pkg.pr.new/vinext@3039

commit: 6162f02

[github-actions]

Performance benchmarks

Compared 6162f02 against base f6cd029 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	3.35 s	3.30 s	⚫ -1.5%
Production build time	vinext	3.75 s	3.74 s	⚫ -0.1%
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}

[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

[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Superseded by consolidated PR #3040.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.