store only status-change events; UI client-side polling refactor

api/openapi.yaml

@@ -195,7 +195,7 @@ paths:
           $ref: "#/components/responses/Unauthorized"
   /api/v1/events/query:
     get:
-      summary: Query stored events
+      summary: Query check status-change history
       operationId: queryEvents
       parameters:
         - name: agent_id
@@ -368,11 +368,16 @@ components:
         accepted:
           type: integer
           minimum: 0
-          description: Number of events stored on this request.
+          description: |
+            Number of events that produced a new status-change row on this request.
         deduplicated:
           type: integer
           minimum: 0
-          description: Number of events whose `event_id` was already known.
+          description: |
+            Number of events that were not stored as a change. Includes events whose
+            `event_id` was already known, events whose `(status, exit_code)` matched
+            the previously observed value for the same check, and events received late
+            (older than the current `last_observed_at` of the check).
     HeartbeatRequest:
       type: object
       additionalProperties: false
@@ -486,7 +491,11 @@ components:
           type: string
           maxLength: 256
     StoredCheckResultEvent:
-      description: Stored event returned by `GET /events/query`. Includes the resolved `agent_id` and server-side `received_at`.
+      description: |
+        Stored status-change event returned by `GET /events/query`. The server persists
+        only events that change `(status, exit_code)` versus the previous observed value
+        for the same `(agent_id, check_id)`. Repeated identical results are not stored.
+        Includes the resolved `agent_id` and server-side `received_at`.
       allOf:
         - $ref: "#/components/schemas/CheckResultEvent"
         - type: object
@@ -537,6 +546,9 @@ components:
           type: integer
         incident_key:
           type: string
+        summary:
+          type: string
+          maxLength: 8192
     Incident:
       type: object
       required: [id, incident_key, state, severity, opened_at]