test(coach): prove the availability probe's SQL against Postgres

The unit suite mocks Prisma, so it proves the discriminant and nothing about the
query underneath it — a wrong column would have left every test green and every
account answering no_data_unconfirmed in production. Seeds the reported case and
the four other shapes: an empty record, another account's rows, tombstoned rows,
and a history that mixes units.

Rounds the out-of-window mean to one decimal, like every other mean the snapshot
surfaces, and annotates a failed manifest probe rather than letting it degrade in
silence.

src/lib/ai/coach/tools/availability.ts

@@ -170,7 +170,10 @@ async function readMeasurementBounds(
             series: row.type as string,
             unit: row.unit,
             count: row._count._all,
-            mean,
+            // One decimal, like every other mean the snapshot surfaces — a raw
+            // float would invite the model to quote a precision the reading
+            // never had.
+            mean: Math.round(mean * 10) / 10,
             min,
             max,
           }

src/lib/ai/coach/tools/inventory.ts

@@ -15,6 +15,7 @@
  * Cost: the manifest is ~0.3–0.5k tokens vs the ~6–15k-token snapshot JSON it
  * replaces — the figures move out of the prompt and into on-demand tool results.
  */
+import { annotate } from "@/lib/logging/context";
 import { isCycleAvailableForUser } from "@/lib/cycle/gate";
 import { buildCoachSnapshot } from "@/lib/ai/coach/snapshot";
 import type {
@@ -274,10 +275,21 @@ async function attachAvailability(
   let probed: Map<string, CoachDomainAvailability>;
   try {
     probed = await probeCoachAvailability(userId, subjects);
-  } catch {
-    // Annotated at the probe; nothing to attach.
+  } catch (err) {
+    // The manifest degrades to the pre-fix precision (every unreached domain
+    // reads "absent"), which is why this is a catch and not a throw — but a
+    // silent one would be the very class of failure this change exists to end.
+    const reason = err instanceof Error ? err.name : "unknown";
+    annotate({
+      action: { name: "coach.inventory.availability_failed" },
+      meta: { probed: subjects.size, reason },
+    });
     return;
   }
+  annotate({
+    action: { name: "coach.inventory.availability" },
+    meta: { probed: subjects.size, stored: probed.size },
+  });
   for (const [key, available] of probed) {
     const entry = keyed.get(key);
     if (!entry) continue;