chore(item-history): fix auth docstring, log AI read failures

Co-authored-by: Orca <help@stably.ai>

src/app/api/v1/quote_items/[id]/item-history/route.ts

@@ -18,7 +18,7 @@ export const dynamic = "force-dynamic";
  *   - `ai` — AI blob only; skip the service call.
  *   - `none` — 404; trigger hides itself.
  *
- * Auth: same as the rest of `/api/v1` (no Bearer required, uses admin PB).
+ * Auth: uses admin PB; no Bearer required (read-only SKU aggregates).
  */
 
 type Mode = "both" | "deterministic" | "ai" | "none";
@@ -76,8 +76,9 @@ export async function GET(
           // Malformed JSON — leave `ai` null and continue.
         }
       }
-    } catch {
-      // Silent: deterministic side still works.
+    } catch (err) {
+      // Deterministic side still works; log so debugging isn't blind.
+      console.warn("[item-history] AI blob read failed:", err);
     }
   }