feat(rules): the staleness sweep — which standing rules assert a fact nobody has confirmed (#3097, milestone 312 step 3)

The query the last two steps were storage for. `rules_due_for_verification`
returns every rule carrying a `verify_with`, ordered by `verified_at` ASC
NULLS FIRST, each row carrying the check IN FULL — the opposite call from
rule_brief, because the reader is about to go and run it.

NULLS FIRST is the ordering this turns on. Postgres sorts NULLs last on an
ASC ordering, which would put the rules nobody has ever confirmed BEHIND
every rule someone once looked at. Exactly backwards: a claim with no
evidence at all outranks an old one.

Rules with no check never appear, and that is the property that keeps the
list worth reading. Most rules are decisions — no truth value, nothing to go
and check. If they appeared here the sweep would be the rulebook.

`mark_rule_verified(rule_id, still_true)` closes the loop, asymmetrically:
passing writes a stamp, FAILING WRITES NOTHING. There is no "verified false"
state because a rule whose check failed is not in a special condition, it is
wrong — and recording the failure as a flag would let it sit there being
false with the sweep satisfied that someone had looked. So it stays at the
top until someone corrects or retires it, and the response says so.

An unrecognised `tier` filter raises rather than falling back. _valid_tier's
silent always_on default is right for a WRITE — a typo should leave a rule
binding — and wrong for a FILTER, where the same fallback quietly answers a
different question and returns a short list that reads as good news.

Deliberately NOT filterable by project: a project reaches rules through
project scope, subscriptions, always-on rulebooks and exclusions, and a
filter missing one of those paths would UNDER-report — the exact failure
this surface exists to prevent. Said so in the docstring rather than
shipping a half-correct filter.

Ownership-scoped like every other rule read (owned rulebook, or owned
project), in ONE statement with an OR across the XOR rather than two queries
merged in Python, so the ordering is the database's and cannot disagree with
itself. Note that rules have no sharing ACL in this schema — no rule_shares,
no rulebook_shares — so there is no wider set for access.py to consult here.

Also fixes a test title that had been lying for ten tools: "all sixteen
tools" asserted 26. The number now lives only in the assertion.

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

tests/test_mcp_tool_rulebooks.py

@@ -217,13 +217,20 @@ async def test_unsubscribe_project_from_rulebook_calls_service():
     assert mock.called
 
 
-def test_register_attaches_all_sixteen_tools():
-    """register(mcp) should call mcp.tool(name=...) for all 16 tools."""
+def test_register_attaches_every_tool():
+    """Every tool in the module reaches the server.
+
+    The count is the guard: a function added to the module but left out of
+    register()'s tuple is invisible to callers and raises nothing. The name
+    said "sixteen" for ten tools' worth of growth — the number lives in the
+    assertion, not the title, so it cannot drift again.
+    """
     from scribe.mcp.tools.rulebooks import register
     mcp = FakeMCP()
 
     register(mcp)
-    assert len(mcp.names) == 26   # +relate_rules/unrelate_rules (milestone 307)
+    # 26 through milestone 307, +2 for the staleness sweep (milestone 312).
+    assert len(mcp.names) == 28
     # spot-check a few names
     assert "list_rulebooks" in mcp.names
     assert "create_rule" in mcp.names
@@ -234,6 +241,9 @@ def test_register_attaches_all_sixteen_tools():
     assert "include_always_on_rulebook" in mcp.names
     assert "create_project_rule" in mcp.names
     assert "suppress_rule_for_project" in mcp.names
+    # milestone 312: the sweep, and the stamp that answers it
+    assert "rules_due_for_verification" in mcp.names
+    assert "mark_rule_verified" in mcp.names
     assert "unsuppress_rule_for_project" in mcp.names
     assert "suppress_topic_for_project" in mcp.names
     assert "unsuppress_topic_for_project" in mcp.names