feat(family): an idea links to the rule topic holding its norms - set_family_topic, the readouts name the rules, the idea row shows the link (milestone 463 step 1 gap, found in step 7, #4993)

Step 1 added family_ideas.topic_id but nothing could set it, so the note<->topic
link the milestone promised existed only as a column. set_family_topic links or
unlinks (0) a topic in a rulebook the caller owns, one idea per topic; the
version does not move. get_family_idea and get_family_adoption list the topic's
rules; list_family_ideas and the Family page name the topic. The model
docstrings no longer claim the topic's rules are platform-scoped in retrieval.

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

tests/test_family_adoption.py

@@ -181,6 +181,6 @@ def test_the_outcomes_the_agent_is_told_are_the_ones_enforced():
 def test_every_adoption_tool_is_classified():
     reads = {"get_family_adoption", "list_family_adoptions"}
     writes = {"assess_family_adoption", "resolve_family_conflict", "revise_family_idea",
-              "set_family_references"}
+              "set_family_references", "set_family_topic"}
     assert reads <= _READ_ONLY_TOOLS
     assert writes <= _WRITE_TOOLS