087 dependency cascade: Flow PT REST finding

Q When an upstream Task's dates move, which downstream Tasks move with it, and does pinned stop it?

Endpoint PUT /entity/tasks/<id> ; POST /entity/tasks/_search

Docs claim Silent on scheduling. The schema types pinned and dependency_violation as checkbox fields and describes neither.

Actual

up -FS-> d1 -FS-> d2,  up -FS-> pin,  up -SS-> ss; every Task written as 2026-03-02..03-03
linked            up 03-02..03-03  d1 03-04..03-05  d2 03-06..03-09  pin 03-04..03-05  ss 03-02..03-03
PUT pin pinned=true -> 200
up due 03-05      up 03-02..03-05  d1 03-06..03-09  d2 03-10..03-11  pin 03-04..03-05 violation=True
up due 03-02      up 03-02..03-02  d1 03-03..03-04  d2 03-05..03-06  pin 03-04..03-05 violation=False
up start 03-09    up 03-09..03-09  d1 03-10..03-11  d2 03-12..03-13  pin (held) violation=True  ss 03-09..03-10
up duration 2400  up 03-09..03-13  d1 03-16..03-17  d2 03-18..03-19  pin (held) violation=True
PUT d1 03-02..03-03 (before up ends)
                  d1 03-02..03-03 pinned=True violation=True   d2 03-04..03-05 (followed d1)
PUT d1 pinned=false
                  d1 03-16..03-17 pinned=False violation=False d2 03-18..03-19
up due 03-20      up 03-09..03-20  d1 03-23..03-24  d2 03-25..03-26  pin (held) violation=True

Teaches

the downstream Task	after an upstream date write
unpinned, any depth	moved to satisfy its dependency, later or earlier, `duration` held
`start-to-start`	follows the upstream start; untouched by a due date write
`pinned` true	dates held; `dependency_violation` true while broken, false again once satisfied
downstream of a pinned Task	follows the pinned Task, not the upstream end of the chain
`finish-to-start`, when a Task with no upstream has its dates written `null`	unmoved; the next real date write moves it (probe 097)

The cascade pulls back as well as pushes. Shortening the upstream moved d1 and d2 earlier. A Task whose dates a person chose and did not pin is overwritten by any upstream write, and by a new edge (probe 092).
Writing a dependent's start_date pins it. The date PUT on d1 set pinned true (as entity_types/Task found) and d2 followed d1 to a date before the upstream ends. That PUT wrote start_date; probe 093 found start_date is what pins, null or real, and a due_date write alone does not. A duration write does not (probe 100); a Task with no upstream never pins (probe 097).
PUT {"pinned": false} reschedules at once: d1 snapped back behind the upstream and d2 with it.
pinned is writable directly, so a sync can protect a Task before it rewrites the upstream end.