TreatmentScheduler deliberately writes only the next session's due_at, because a
date not yet anchored to anything real is a false claim about the future and has
to be rewritten every time a patient runs late. But the panel still needs to
show the whole course.
TreatmentPlanProjector builds that chain at display time and writes nothing.
Each date carries is_estimate so a projection is never mistaken for a fact. A
session's anchor is, in order: when it was finished, when its appointment is, or
its written due_at; a case with none falls back to when it was opened, so a
course that has not been booked yet still shows dates instead of blanks.
Read and write stay in separate classes — mixing them risks storing an estimate.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
