Monitoring: implementation status, and the compat test for INBUXA's data (test 26)

monitoring_compat, ignored, checks the observed settings against a copy
of INBUXA's data, reads the old history without an error, and purges it.
The status names where each part lives, which suite covers each
acceptance test, the tests not exercised, and the known limits.

docs/spec/features/monitoring.md

@@ -530,6 +530,40 @@ these needs a write.
     domains' traces is wanted (MON-31).
 12. Size of INBUXA's `o` and `x` subspaces, to check MON-19's estimate.
 
+## Implementation status
+
+Built 2026-09-19 from this spec, clean-room, under the multi-tenancy hand-off
+brief's rules. Metric history is in `crates/common/src/telemetry/metrics/store.rs`,
+trace history in `crates/common/src/telemetry/tracers/store.rs`, alerts in
+`crates/common/src/telemetry/alerts.rs`, the live streams in
+`crates/http/src/live.rs`, and `x:Metric` and `x:Trace` in
+`crates/jmap/src/inbuxa/telemetry.rs`, at the paths the shared tests name;
+upstream files carry hooks marked `inbuxa:`. All four suites in
+`tests/src/telemetry` are un-gated and pass, so the table above is history:
+they cover tests 10 and 12 (`tracing.rs`), 13 (`metrics.rs`) and 18
+(`alerts.rs`). Tests 1, 3, 5 to 9, 11, 14 to 17, 19 to 21, 23 and 24 pass as
+`tests/src/system/monitoring.rs`.
+
+- **MON-1 to MON-39:** built, with the limits below.
+- **Test 26 (compat)** is written as `monitoring_compat`, ignored, and unrun
+  until a copy of INBUXA's data is provided. It checks observed 1, reads the
+  old history without an error, and purges it. It deletes history, so only
+  ever run it against a copy.
+- **Not exercised by a test:** 2 (an unreachable PostgreSQL tracing store),
+  4 (`queue.count` after a restart; the gauge is set from the queue on each
+  calculation), 22 (a webhook for `telemetry.alert-event`; webhooks are the
+  shared, unchanged path), 25 (a full buffer; the subscriber is lossy by
+  construction), and test 17's 30-minute close.
+- **Known limits, not requirements of this spec:**
+  - A trace cut at 1000 events (MON-15) carries the number cut as a `total`
+    value on its closing event, since no event type fits a separate marker.
+  - The `inbuxa:admin` scope check on live tokens (MON-23) waits for the auth
+    contract; until then the permission and server-level checks apply.
+  - A live token can be reused within its 60 seconds (Decision, MON-23).
+  - The alert edge trigger (MON-26) is held in memory, so an alert whose
+    condition holds across a restart fires once more.
+  - The stream limit (MON-24) is per node.
+
 ## Observed
 
 Settled on 2026-09-18 against INBUXA's live Enterprise server (Stalwart