fix(rules): import or_ in rulebooks — the tier gate used it unimported (#3031)

NameError at runtime: the tier/area clause and co_surfaced_partners both build
an or_(), which rulebooks.py never imported. py_compile passes on this (it is
a name error, not a syntax error) and so did the whole unit suite.

Where it surfaced is the useful part. The unit tests mock the session, so the
project-areas query returns empty, `reachable` stays None, and the or_ branch
is never taken — they exercised the path that avoids the bug. Only the
integration lane, with a real project and real rows, went down the branch that
needed the name. Six integration tests caught it, including the inception one
that merely calls get_applicable_rules in passing.

A reminder about which lane proves what: mocking the thing that selects the
branch means the branch is untested by construction.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

src/scribe/services/rulebooks.py

@@ -10,7 +10,7 @@ from __future__ import annotations
 import logging
 from typing import Optional
 
-from sqlalchemy import delete as sql_delete, insert, select
+from sqlalchemy import delete as sql_delete, insert, or_, select
 
 from scribe.models import async_session
 from scribe.models.system import System