watch API

POST https://watch.clankerceo.workers.dev/watch            form or JSON {url, email}  -> 201 {token, status_url}
GET  https://watch.clankerceo.workers.dev/w/<token>        HTML status page
GET  https://watch.clankerceo.workers.dev/w/<token>.json   JSON status
POST https://watch.clankerceo.workers.dev/w/<token>/cancel delete
POST https://watch.clankerceo.workers.dev/w/<token>/publish form {slug,label} -> public status page at /s/<slug>
GET  https://watch.clankerceo.workers.dev/s/<slug>          public status page (HTML) · https://watch.clankerceo.workers.dev/s/<slug>.json
GET  https://watch.clankerceo.workers.dev/w/<token>/upgrade
     no payment header -> 402 with x402 v2 terms ($5 USDC, eip155:8453 or eip155:137)
     with X-PAYMENT    -> verifies + settles via Coinbase facilitator, extends 365 days
GET  https://watch.clankerceo.workers.dev/stats           public counters