fix(6470): a moment proposal counts only opens no hook explained, and asks the reader to judge it

The signal counted every get_rule open against every moment from the
previous three minutes, so a rule a search arm had just shown was
proposed for whatever moment happened to fire. All nine pending signal
proposals were wrong.

- The hook skips an open of a rule a hook named this session, and sends
  the last three acts from 90 seconds instead of 30 from 180.
- A rule already mounted anywhere gathers no signal evidence.
- A signal pair keeps the actions that reached its moment and shows them
  as its why.
- The proposal line says it is co-occurrence, not a recommendation, and
  asks the reader to check the rule against the moment before offering
  it; moments.md says the same.

Plugin 2026.10.26.2029.

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

tests/test_integration_rule_moment_judgments.py

@@ -195,7 +195,23 @@ async def test_the_open_resolves_acts_through_the_installs_mappings(world):
     out = await judgments_svc.opened_after(uid, done.id, acts, session_id="s1")
     assert "work.deliver" in out["moments"]
     assert "work.run" not in out["moments"]
-    assert (await _row(done.id, "work.deliver")).source == "signal"
+    row = await _row(done.id, "work.deliver")
+    assert row.source == "signal"
+    # The action that reached the moment is kept, and shown as the why.
+    assert row.evidence["reached_by"] == {"git push": 1}
+    assert row.note.startswith("Opened just after `work.deliver` (reached by `git push`)")
+
+
+async def test_a_rule_already_mounted_gathers_no_signal(world):
+    """A mounted rule arrives by lookup at its own moments, so an open of it
+    is no evidence it is missing another."""
+    uid, done = world["uid"], world["done"]
+    await rulebooks_svc.set_rule_moments(done.id, uid, ["work.finish"])
+    for situation in ("a", "b", "c", "d"):
+        assert await judgments_svc.co_occurred(
+            uid, done.id, ["work.verify"], situation=situation,
+        ) == ""
+    assert await _row(done.id, "work.verify") is None
 
 
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