fix(measurements): read the GKI's glucose from the ketone side

The correlated EXISTS over a time range had no equality to drive it from the ketones, so a person with years of sensor glucose walked every glucose row in the window. Each ketone reading now reads its glucose through a LATERAL index range. A full tie between two glucose readings resolves by id, the day tile names the unit, and the empty text says a ketone reading above zero.

docs/api/openapi.yaml

@@ -904,7 +904,8 @@ paths:
       tags:
         - Cycle
       summary: Change the calendar subscription's options (#1350)
-      description: Field-by-field update of the options. The URL does not change; the feed's next fetch serves the new content.
+      description: Field-by-field update of the options. The URL does not change; the feed's next fetch serves the new
+        content. A change saved while the link is being replaced applies to the link that stays live.
       requestBody:
         required: true
         content:
@@ -927,6 +928,13 @@ paths:
             application/json:
               schema:
                 $ref: "#/components/schemas/ErrorEnvelope"
+        "409":
+          description: The link was replaced twice while the change was being saved (`cycle.feed.exists`); nothing changed, and
+            sending it again applies it to the link that is live now.
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/ErrorEnvelope"
         "422": *a4
         "429": *a12
     delete:
@@ -959,7 +967,8 @@ paths:
       summary: Replace the calendar subscription's link (#1350)
       description: "One transaction: the live link is revoked and a new one minted with the same options, the forecast style
         included. Returns the new URL EXACTLY ONCE. Calendars using the old link stop updating. Of two rotations racing,
-        the one that loses answers 409 `cycle.feed.exists` and the winner's link stands."
+        the one that loses answers 409 `cycle.feed.exists` and the winner's link stands; a rotation racing the
+        subscription being turned off answers 404 `cycle.feed.none` and the subscription stays off."
       responses:
         "201": *a13
         "401": *a14