Mark the caller's mini-app session as a Farcaster sign-in.

The mini-app signs in with a wallet (SIWE -> register-viewer), which is also how an agent makes an account, so that session cannot tell a person in Farcaster from an agent. This takes the caller's existing jj_ session plus a Farcaster Quick Auth token, verifies the token against Farcaster's published keys (issuer, this app's domain, expiry), and returns a fresh session for the SAME profile and wallet carrying the FID. Nothing else about the session changes: same scope, same wallet, so payments work as before.

The mark opens the people's discovery listing (GET /v2/media/discover and the chat's media_search), where a creator who turned AI agent discovery off still appears; each piece's own Private setting still applies.

Only a full ("session") jj_ token can be marked: no Firebase cookie, no platform or agent key, no OAuth bearer, no "viewer" token. Nothing is written to the database.