The engagement letter records when the client opened it

A matter notebook runs in the firm's container. The engagement letter is one page in it. The client is a guest of the notebook and a viewer of that one page; every other node in the matter tree answers them with a 403.

When the client opens the page, their viewer posts an opened interaction, and the notes service keeps firstOpenedAt and lastOpenedAt per collaborator. The version list shows revision 4 created at 09:12 and revision 5 at 11:05. The client's first open is 09:40, so what they read was revision 4, and revision 4 is immutable.

The practice-management script reads two URLs and writes one line in the file: who opened it, when, which revision. No tracking pixel, no "please confirm receipt", no PDF plugin that phones home.

The reading record lives in the same store as the document.