Render unhealthy-age rollup on the Waterline dashboard

Surfaces `operator_metrics.tasks.oldest_unhealthy_at` and
`operator_metrics.tasks.max_unhealthy_age_ms` on the Unhealthy tasks
card so operators can read the worst-case duplicate-risk task age
(the earliest of `oldest_dispatch_failed_at`, `oldest_claim_failed_at`,
`oldest_dispatch_overdue_since`, `oldest_lease_expired_at`) from a
single meta line above the existing per-path detail rows instead of
taking a max over four separate age fields themselves.

`dashboard.vue` adds `operatorUnhealthyAgeAvailable()` /
`operatorUnhealthyOldestAt()` helpers and a v-if-guarded summary line:

worst <duration> unhealthy (since <ISO>)

The line degrades gracefully when the snapshot predates the rollout-
safety contract: the helper returns false when `max_unhealthy_age_ms`
is missing or null and the existing per-path age detail rows still
surface individual lease, dispatch-overdue, and dispatch-failed ages.

`testIndexExposesUnhealthyAgeRollup` pins the rollup keys on the
Waterline stats payload so a downstream regression that drops the
keys trips the test instead of silently disappearing from the
dashboard. The test self-skips when the vendored workflow package
predates the contract, mirroring `testIndexExposesBackendSeverityRollup`.

Author: durable-workflow-ops

resources/js/screens/dashboard.vue

@@ -314,6 +314,12 @@
                                     {{ operatorMetricLabel('tasks', 'dispatch_overdue') }} dispatch overdue,
                                     {{ operatorMetricLabel('tasks', 'lease_expired') }} lease expired
                                 </div>
+                                <div v-if="operatorUnhealthyAgeAvailable()" class="wl-operator-metric__meta">
+                                    worst {{ operatorDurationMetricLabel('tasks', 'max_unhealthy_age_ms') }} unhealthy
+                                    <template v-if="operatorUnhealthyOldestAt()">
+                                        (since {{ operatorUnhealthyOldestAt() }})
+                                    </template>
+                                </div>
                                 <div v-if="operatorStuckLeaseAgeAvailable()" class="wl-operator-metric__meta">
                                     oldest lease {{ operatorDurationMetricLabel('tasks', 'max_lease_expired_age_ms') }} expired
                                     <template v-if="operatorStuckLeaseOldestExpiredAt()">
@@ -1351,6 +1357,24 @@ export default {
             return tasks.oldest_dispatch_failed_at || null;
         },
 
+        operatorUnhealthyAgeAvailable() {
+            const tasks = (this.operatorMetrics && this.operatorMetrics.tasks) || {};
+
+            if (tasks.max_unhealthy_age_ms === undefined
+                || tasks.max_unhealthy_age_ms === null) {
+                return false;
+            }
+
+            return Number(tasks.unhealthy || 0) > 0
+                || Number(tasks.max_unhealthy_age_ms || 0) > 0;
+        },
+
+        operatorUnhealthyOldestAt() {
+            const tasks = (this.operatorMetrics && this.operatorMetrics.tasks) || {};
+
+            return tasks.oldest_unhealthy_at || null;
+        },
+
         operatorSchedulesAvailable() {
             const schedules = this.operatorMetrics && this.operatorMetrics.schedules;
 

tests/Feature/V2DashboardStatsControllerTest.php

@@ -959,6 +959,36 @@ public function testIndexExposesMatchingRole(): void
         );
     }
 
+    public function testIndexExposesUnhealthyAgeRollup(): void
+    {
+        config()->set('waterline.engine_source', 'v2');
+
+        $response = $this->get('/waterline/api/stats')->assertStatus(200);
+
+        $tasks = $response->json('operator_metrics.tasks');
+
+        $this->assertIsArray($tasks);
+
+        if (! array_key_exists('oldest_unhealthy_at', $tasks)
+            || ! array_key_exists('max_unhealthy_age_ms', $tasks)) {
+            $this->markTestSkipped(
+                'Vendored workflow package predates the unhealthy-age rollup '
+                . '(operator_metrics.tasks.{oldest_unhealthy_at,max_unhealthy_age_ms}).',
+            );
+        }
+
+        $this->assertTrue(
+            $tasks['oldest_unhealthy_at'] === null
+                || is_string($tasks['oldest_unhealthy_at']),
+            'operator_metrics.tasks.oldest_unhealthy_at must be null or ISO-8601 string',
+        );
+        $this->assertTrue(
+            $tasks['max_unhealthy_age_ms'] === null
+                || is_int($tasks['max_unhealthy_age_ms']),
+            'operator_metrics.tasks.max_unhealthy_age_ms must be null or integer milliseconds',
+        );
+    }
+
     public function testIndexExposesBackendSeverityRollup(): void
     {
         config()->set('waterline.engine_source', 'v2');