While I'm not sure how they've integrated it so far, I imagine browsers will either implement a plugin API for extensions to handle passkeys, or 1p can override the webauthn api and fallback to the browser when a website is authenticating.
Passwordless future definitely wasn't here just 1-2 years ago. The management of WebAuthn Discoverable Credentials / Resident Keys was so fucking awful on every platform I tested them on.
You want to clear your Resident Key for a website on Windows? Command-line.
While I'm not sure how they've integrated it so far, I imagine browsers will either implement a plugin API for extensions to handle passkeys, or 1p can override the webauthn api and fallback to the browser when a website is authenticating.