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/services/family_adoption.py

@@ -545,8 +545,7 @@ async def assessment_precedents(user_id: int, project_id: int, idea_id: int,
     for d, idea_title, project_title in rows:
         if not await access.can_read_project(user_id, d.project_id):
             continue
-        item = d.to_dict()
-        item.update({"idea_title": idea_title, "project_title": project_title})
+        item = {**d.to_brief(), "idea_title": idea_title, "project_title": project_title}
         if d.idea_id == idea_id:
             item["relation"] = "same idea, another project"
             out_same.append(item)