refactor(cache): defer adapter initialization

[james-elicx]

Part 3 of 16 in the staged CDN adapter stack. Depends on #3142.

Summary

• makes declarative data-cache and CDN-adapter registration lazy and safe across duplicated stage module graphs
• keeps imperative cache handlers authoritative for backwards compatibility
• avoids pulling the data-cache implementation into an uncached request entrypoint until middleware actually uses it

Validation

• focused cache-adapter and CDN-cache tests
• focused format, lint, and type checks
• cumulative exact-tip changed-test sweep: 3,461 passed, 2 skipped

Review size

• Implementation: +178 / -22 LOC
• Tests and fixtures: +196 / -11 LOC
• Other (docs, config, lockfile): +0 / -0 LOC
• 8 changed files

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

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/@vinext/cloudflare@3143

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npm i https://pkg.pr.new/@vinext/types@3143

npm i https://pkg.pr.new/vinext@3143

commit: 030335e

[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 030335e against base b614b12 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	142.3 KB	142.3 KB	⚫ +0.0%
Client entry size (gzip)	vinext	129.6 KB	129.6 KB	⚫ -0.0%
Dev server cold start	vinext	3.04 s	3.02 s	⚫ -0.9%
Production build time	vinext	3.29 s	3.29 s	⚫ -0.2%
RSC entry closure size (gzip)	vinext	119.2 KB	119.7 KB	⚫ +0.5%
Server bundle size (gzip)	vinext	202.8 KB	203.4 KB	⚫ +0.3%

View detailed results and traces

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