Structured logging with the X-GitHub-Delivery correlation id

Two independent reviews landed on the same gap: logging is bare console.log/warn/error with ad-hoc prefixes ([Stale Bot], GitHub API call failed...), and the correlation id GitHub hands us for free — the X-GitHub-Delivery header — is never read.

Proposal: one log(level, event, fields) helper emitting a single JSON object per line, which Cloudflare indexes:

{ "level": "warn", "event": "github_api_retry", "delivery": "8ad0...",
  "repo": "openwrt/packages", "pr": 1234, "installation": 456,
  "method": "GET", "endpoint": "/repos/.../commits", "status": 503,
  "attempt": 2, "budget_used": 31, "deploy": "d8f0c4e" }

Worth carrying on every line: delivery id, event/action, repo, PR or issue number, installation id, head SHA, and for API calls the operation, attempt, status and remaining budget. That turns "why did this PR behave oddly" into one filter on delivery=... covering the whole lifecycle — token, config, commits, validators, labels, comment, check-runs.

Not urgent, but it is the difference between reading logs and grepping them.

Start by locating the existing console.log/warn/error calls and the request-handling path where X-GitHub-Delivery is available. Trace the token, config, commits, validators, labels, comment, and check-runs lifecycle to define the fields each event needs. Done means one JSON object per line with the requested correlation and operation fields, indexed by delivery id.