fix(family): a decision read as precedent says its reason once - to_brief for precedents and idea history; the decision log keeps the full row (#5131)

Each decision stored its reason three times (reason, before.reason, after.reason)
and a promotion carried the whole criteria reasoning in evidence. Precedents
(assess, promote, get_family_adoption, get_family_idea) and get_family_idea's
history now serve FamilyDecision.to_brief(): reason once, before/after as status,
canon_version and platforms, evidence as the cited list. list_family_decisions
and the decision echoed back by a write keep to_dict. The precedent count was
already bounded at five.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/scribe/models/family.py

@@ -357,3 +357,37 @@ class FamilyDecision(Base, CreatedAtMixin):
             "user_id": self.user_id,
             "created_at": iso(self.created_at),
         }
+
+    def to_brief(self) -> dict:
+        """The decision as a reader WEIGHING it needs it: what was decided,
+        why — once — and the state it moved between.
+
+        Precedents and an idea's history are read in bulk, a handful per
+        call, and the full row repeats itself: an assessment's reason is
+        stored again inside `after` (and the prior one inside `before`), and
+        a promotion's evidence carries the whole criteria reasoning. So a
+        state here is its status, version and platforms only, and evidence is
+        the cited list alone (#5131). The full row is `to_dict`, which the
+        decision log serves.
+        """
+        return {
+            "id": self.id,
+            "idea_id": self.idea_id,
+            "project_id": self.project_id,
+            "action": self.action,
+            "reason": self.reason,
+            "before": _brief_state(self.before),
+            "after": _brief_state(self.after),
+            "evidence": list((self.evidence or {}).get("evidence") or []),
+            "created_at": iso(self.created_at),
+        }
+
+
+# What a decision's before/after keeps in its brief: the state, not the prose.
+_BRIEF_STATE_KEYS = ("status", "canon_version", "platforms")
+
+
+def _brief_state(state: dict | None) -> dict | None:
+    if state is None:
+        return None
+    return {k: state[k] for k in _BRIEF_STATE_KEYS if k in state}