Raise Cloudflare WordPress boot CPU budget

[chubes4]

Summary

• declare Cloudflare's paid-plan five-minute CPU allowance for the WordPress boot gate
• preserve the fixed 128 MB isolate memory limit
• add deterministic coverage for the deployment limit and document why it is required

Follow-up to #1856 and #1838.

Remote evidence

The merged Worker deployed successfully at https://wp-codebox-cloudflare-runtime.chubes.workers.dev with a 17 ms startup time and a 21,313.72 KiB / 7,950.82 KiB gzip bundle. Real requests then returned Cloudflare error 1102, which Cloudflare documents as resource exhaustion. The paid Workers default is 30 seconds of CPU per request; the supported maximum is five minutes via limits.cpu_ms: 300000. Memory remains fixed at 128 MB.

Cloudflare reference: https://developers.cloudflare.com/workers/platform/limits/#cpu-time

How to test

1. Check out this branch from a fresh clone and run npm ci.
2. Run npm run build.
3. Run npm run test:cloudflare-runtime; expect both envelope and CPU-budget tests to pass.
4. Run npm run cloudflare:local-gate; expect two HTTP 200 health envelopes and automatic cleanup.
5. Run npm run cloudflare:dry-run; expect the reviewed bundle size and no resource mutation.
6. Run git diff --check.

Compatibility

This changes only the deployed Cloudflare Worker's CPU allowance. WP Codebox runtime contracts, extension paths, local workerd behavior, and Cloudflare's 128 MB memory limit are unchanged.

AI assistance

• AI assistance: Yes
• Tool(s): OpenCode with gpt-5.6-sol
• Used for: Diagnosed the remote Cloudflare 1102 response, added the explicit deployment limit and regression coverage, and verified the follow-up with Chris; Chris reviews and owns the change.