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/mcp/tools/family.py

@@ -33,7 +33,8 @@ async def list_family_ideas(
 
 async def get_family_idea(note_id: int) -> dict:
     """One family idea with what an evaluation needs: its state, platforms,
-    full decision history, ledger counts, THE THREE CRITERIA, the `ledger`
+    decision history (brief — each reason once; list_family_decisions has
+    the full rows), ledger counts, THE THREE CRITERIA, the `ledger`
     (every project's answer, with `needs_recheck`), and the `precedents` —
     the decisions on the ideas nearest this one by meaning.
     Read the precedents before deciding, and decide consistently with them