The one way to change a loan's stage.

Send the stage KEY, never the display name. Teams rename stages —
"Contract Executed" becomes "Application" — and a key does not move when
they do. GET /api/partner/loan-stages lists the keys.

What a transition publishes. A stage move emits loansStageUpdated,
plus loansFunded when the destination is the funded stage and
loansClearToClose when it is clear-to-close. Subscribers that care only
about funding do not have to inspect every move.

Terminal stages. Moving to a terminal stage records the outcome; the
loan leaves the active pipeline but stays readable.

Board order. beforeId is the loan that should sit immediately below
this one after the drop. Omit it to append to the column (a loan-file
click). Send it — including as null for the end of the column — when
dragging on the pipeline board, so a same-column reshuffle is saved.