callbackMint now takes the connection: custody_only is a connect for a
managed-connection-only provider bound to connection.kind creator with a
targetId. Anything else is refused at start with creator_connection_required
before any redirect, and at the callback from the signed state before the
code exchange. The streampixels profile note says what Heimdall guarantees
and records the S1 rule that SP's redeem treats a non-creator Joystick
completion as an error, never a sign-in.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>