pages-function-checkpoint-debug

When a Cloudflare Pages Function (or any Worker-style serverless handler) returns a generic 502/500 hiding the actual error, instrument the handler with a ?debug=1 query param + an in-memory checkpoint array that accumulates step markers and gets returned in the response body. Lets you bisect "which step crashed" in 1-2 deploy/retest cycles instead of guessing for hours.