feat(moments): mounted rules arrive when their moment happens, through every door (milestone 458 step 4a, #4922)

A rule mounted on a moment now reaches the session when an act reaches
that moment, with no semantic match involved:

- run_moment_arm on the pipeline: a lookup, not a ranked search. Each
  line names the moment and the act that reached it ("at work.deliver,
  reached by `git push`"), so a misfire is visible where it lands and
  can be unmapped in-session. A repeat is cited, not quoted; fresh
  rules are recorded surfaced under source moment_rule with the moment
  in detail. No retrieval_logs row, as for the other lookups, so no
  latency is persisted for this arm.
- rule_scope: a rule's home clause, moved out of semantic_search_rules
  so the moment lookup scopes by the same one.
- rulebooks.rules_on_moments / mounted_moments.
- The plugin door: a catch-all PreToolUse hook (scribe_moment.sh). It
  keeps /moment-tools' answer on disk for five minutes, so a call to a
  tool that cannot reach a mounted rule sends nothing, and an install
  that has mounted nothing sends one request per window. It shares the
  rules ledger with the other arms and fails open silently.
- The MCP door: Scribe's own tools named by the shipped mappings carry
  moment_rules in their response, so a client without the plugin gets
  them too. The hook skips those tools. A guard pins the attach on
  every one.

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

tests/conftest.py

@@ -215,6 +215,26 @@ def _no_lesson_rule_links(request):
         yield
 
 
+@pytest.fixture(autouse=True)
+def _no_moment_delivery(request):
+    """Stub the moment lookup the mapped MCP tools attach (milestone 458).
+
+    update_task, the create_* record tools and the milestone tools now hand
+    back the rules mounted on the moment they mark, and finding those is two
+    database reads. Patched BENEATH the attach, at `deliver_for_act`, because
+    the tools bind `attach_moment_rules` by name at import time. Skipped for
+    integration tests; tests/test_moment_delivery.py binds the real one.
+    """
+    if request.node.get_closest_marker("integration"):
+        yield
+        return
+    from scribe.services.retrieval_pipeline import RuleResult
+
+    with patch("scribe.services.moment_delivery.deliver_for_act",
+               AsyncMock(return_value=([], RuleResult()))):
+        yield
+
+
 @pytest.fixture(autouse=True)
 def _no_rule_arm():
     """Stub the write-path hint's standing-RULES arm (milestone 307).