Record that this lead booked its call.

Admin-gated exactly like the reader above, and for the same reason: the lead table is an audit trail of attestations, and who may write on one is the same question as who may read one.

It exists because nothing else can know. The booking happens on Calendly, which does not call us back, so the only thing that can say a call was booked is the person who saw it appear in their calendar. What the stamp BUYS is the reminder: partner_lead_nudge will not chase a row whose call is booked, so this is how an operator stops a letter that would otherwise ask a partner to book a meeting they are already coming to.

Idempotent. Clicking it twice is an operator clicking it twice, and the first time is the one that is true, so a second call succeeds and changes nothing.