feat(moments): rules mount on moments, through every rule door (milestone 458 step 3, #4921)

rule_moments (migration 0117) records which moments a rule arrives at, by
catalog name, cascading with the rule. rule_detail, the one seam every
rule door already returns through, gains moments beside system_ids: None
leaves the mounts alone, a list replaces them. get_rule and both
list_rules doors read them back, batched per page.

All five MCP rule/preference writes and the three REST ones take moments
and validate them before their create or update. An unknown name is
refused with the catalog listed and leaves no half-made rule behind; a
parity test pins that ordering on every door.

Backup v22 carries the mounts as a join table remapped through the rule
map; a real-Postgres round trip checks they land on the restored rule.

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

tests/helpers.py

@@ -315,7 +315,7 @@ def plain_rule_detail():
     stubbing the seam slightly differently is a test asserting something
     slightly different than it appears to.
     """
-    async def _detail(_uid, rule, _system_ids=None):
+    async def _detail(_uid, rule, _system_ids=None, _moments=None):
         return rule.to_dict()
     return patch("scribe.mcp.tools.rulebooks.rulebooks_svc.rule_detail", _detail)