feat(moments): the human door onto mounts, mappings and per-moment telemetry (milestone 458 step 6, #4924)

Everything an agent can do with moments, a person can now see and change
in the app.

- Rule editor: a moment picker beside the trigger. Catalog moments are
  ticked; a named procedure's `skill.<name>` is typed and checked as the
  server checks it. `moments` is always sent, so unticking the last moment
  unmounts the rule.
- Settings, Moments section (General tab): for each moment, what it
  means, the actions that reach it on this install (shipped ones can be
  switched off, the install's own removed), how many rules are mounted on
  it, and deliveries and agent opens over the window. Below that: named
  procedures with mounts, switched-off defaults with Restore, and a form to
  add an action.
- retrieval_telemetry.moment_usage: per moment, `delivered`, `rules`,
  `opened` (agent pulls after the first delivery there; an upper bound, as
  by_source is) and `last_delivered_at`. No ratio, because a mount is a
  person's statement, not a ranker's guess. Guarded on its own, and also
  reported in retrieval_summary as `moment_usage`.
- rulebooks.mount_counts; mounted_moments now derives from it.
- GET /api/retrieval/moments carries `mounted` and `usage` (?days=).
  DELETE /moments/mappings also reads the mapping from query parameters,
  since the browser's DELETE sends no body.

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

tests/test_integration_rule_moments.py

@@ -199,3 +199,64 @@ async def test_the_delivery_lookup_answers_by_home(world):
     # The plugin's "can anything arrive" answer spans every home.
     assert await rulebooks_svc.mounted_moments(uid) >= {"work.finish", "reply.report", "work.deliver"}
     assert not (await rulebooks_svc.mounted_moments(sid)) & {"work.finish", "work.deliver"}
+
+    # Counted the same way for the Settings view: a rule mounted twice counts
+    # once per moment, and another user's mounts are not in the count.
+    counts = await rulebooks_svc.mount_counts(uid)
+    assert counts.get("work.deliver", 0) >= 1 and counts.get("reply.report", 0) >= 1
+    assert set(counts) == await rulebooks_svc.mounted_moments(uid)
+    assert not set(await rulebooks_svc.mount_counts(sid)) & {"work.finish", "work.deliver"}
+
+
+async def test_moment_usage_counts_deliveries_and_the_agent_opens_that_followed(world):
+    """The per-moment readout (step 6), on real SQL: an EXISTS inside a
+    COUNT(CASE …) is a shape no mock can vouch for, and the block's own guard
+    would turn a database refusal into a quiet `moment_usage_failed`."""
+    from datetime import datetime, timedelta, timezone
+
+    from sqlalchemy import delete
+
+    from scribe.models.rule_usage import PULLED, SURFACED, RuleUsageEvent
+    from scribe.services.retrieval_pipeline import MOMENT_RULE_SOURCE
+    from scribe.services.retrieval_telemetry import moment_usage
+
+    uid, sid, rule = world["uid"], world["sid"], world["rule"]
+    other = await rulebooks_svc.create_rule(
+        rule.topic_id, uid, "Close the task with the push",
+        "A task closes in the turn its CI goes green.",
+        when_to_apply="the CI run on a pushed commit has just gone green",
+    )
+    now = datetime.now(timezone.utc)
+
+    def ev(user, rule_id, event, source, ago, detail=None):
+        return RuleUsageEvent(user_id=user, rule_id=rule_id, event=event, source=source,
+                              detail=detail, created_at=now - ago)
+
+    async with async_session() as s:
+        await s.execute(delete(RuleUsageEvent).where(RuleUsageEvent.user_id.in_([uid, sid])))
+        s.add_all([
+            ev(uid, rule.id, SURFACED, MOMENT_RULE_SOURCE, timedelta(hours=3), "work.finish"),
+            ev(uid, rule.id, SURFACED, MOMENT_RULE_SOURCE, timedelta(hours=2), "work.finish"),
+            ev(uid, other.id, SURFACED, MOMENT_RULE_SOURCE, timedelta(hours=1), "work.finish"),
+            ev(uid, rule.id, SURFACED, MOMENT_RULE_SOURCE, timedelta(hours=1), "reply.report"),
+            # An agent opened `rule` after its first work.finish delivery, and
+            # BEFORE its reply.report one — so it counts at the first only.
+            ev(uid, rule.id, PULLED, "mcp_get_rule", timedelta(minutes=150)),
+            # A person opening `other` in the browser is not an agent open.
+            ev(uid, other.id, PULLED, "rest_rule", timedelta(minutes=5)),
+            # A ranked surfacing is not a delivery at a moment.
+            ev(uid, other.id, SURFACED, "pre_tool_rule", timedelta(minutes=5)),
+            # Nor is a delivery older than the window, or someone else's.
+            ev(uid, other.id, SURFACED, MOMENT_RULE_SOURCE, timedelta(days=3), "work.deliver"),
+            ev(sid, rule.id, SURFACED, MOMENT_RULE_SOURCE, timedelta(minutes=5), "work.finish"),
+        ])
+        await s.commit()
+
+    block = await moment_usage(uid, now - timedelta(days=1))
+    assert "moment_usage_failed" not in block
+    assert set(block["by_moment"]) == {"work.finish", "reply.report"}
+    finish = block["by_moment"]["work.finish"]
+    assert (finish["delivered"], finish["rules"], finish["opened"]) == (3, 2, 1)
+    report = block["by_moment"]["reply.report"]
+    assert (report["delivered"], report["rules"], report["opened"]) == (1, 1, 0)
+    assert report["last_delivered_at"]