Improve handling of alerts when no active alerts are present

docs/integrations/weatherapi.md

@@ -28,9 +28,14 @@ Every response used by the adapter must be JSON with a top-level `data` field:
 }
 ```
 
-`data: null` is treated as a missing source. Missing optional sources follow the
-configured missing-source policy. Missing hourly forecast data fails bundle
-fetching because hourly periods are required for report generation.
+For most sources, `data: null` is treated as a missing source. Missing optional
+sources follow the configured missing-source policy. Missing hourly forecast
+data fails bundle fetching because hourly periods are required for report
+generation.
+
+`/alerts/active` is the exception: a successful response with `data: null`
+means the endpoint was checked and there are no current active alerts. The
+adapter records a non-missing alerts source and an empty alert run.
 
 Malformed JSON envelopes, non-2xx statuses, and response read failures include
 endpoint context in returned errors. Decode errors include source context when
@@ -92,9 +97,14 @@ Policy behavior:
 - `warn`: omit the source data, add a warning, and continue
 - `none`: omit the source data and continue without a warning
 
+For `/alerts/active`, an HTTP error or missing `data` field still fails or
+follows the relevant error path, but explicit `data: null` is not a
+missing-source condition.
+
 ## Source Identity
 
-For non-null source payloads, the adapter records:
+For source payloads accepted into the bundle, including the explicit `null`
+alerts payload, the adapter records:
 
 - source name
 - endpoint path

docs/internal/weather-data.md

@@ -53,8 +53,9 @@ contract used by this project.
 
 The adapter records source name, endpoint, query, fetch time, source timestamps
 when available, SHA-256 hash over compact raw `data` JSON, missing status, and
-source warnings. `app.FetchAndSaveBundle` can write bundle JSON atomically for
-inspection.
+source warnings. Successful `data: null` responses from `/alerts/active`
+represent a checked empty active-alert list, not a missing source.
+`app.FetchAndSaveBundle` can write bundle JSON atomically for inspection.
 
 ## Skip And Resume Behavior
 
@@ -69,6 +70,8 @@ data is required and cannot be skipped.
   endpoint context.
 - Missing hourly data or hourly forecasts with no periods fail bundle fetch.
 - Optional and stub sources follow missing-source policy.
+- Explicit `data: null` from `/alerts/active` produces an empty, non-missing
+  alert run.
 
 ## Tests