Render run-summary projection missing-run age on the Waterline dashboard

Surfaces operator_metrics.projections.run_summaries.{oldest_missing_run_started_at,max_missing_run_age_ms}
on the Projection health card so operators can read run-summary
projection-lag age directly from the dashboard alongside the existing
"X summaries for Y runs, M missing, O orphaned, S stale" rollup. The
new line reads "Oldest run-summary missing run X behind (since ISO)"
and is gated by operatorRunSummaryMissingAgeAvailable() so pre-contract
workflow alphas that omit the pair render nothing rather than zeros or
nulls.

Adds operatorProjectionDurationMetricLabel(group, key) helper that
mirrors operatorDurationMetricLabel for the projections section.

Adds testIndexExposesRunSummaryMissingAge to V2DashboardStatsControllerTest
pinning the two keys on operator_metrics.projections.run_summaries and
self-skipping when the vendored workflow alpha predates the
rollout-safety contract.

Author: durable-workflow-ops

resources/js/screens/dashboard.vue

@@ -412,6 +412,12 @@
                                 {{ operatorProjectionMetricLabel('orphaned') }} orphaned,
                                 {{ operatorProjectionMetricLabel('stale') }} stale.
                             </p>
+                            <p v-if="operatorRunSummaryMissingAgeAvailable()">
+                                Oldest run-summary missing run {{ operatorProjectionDurationMetricLabel('run_summaries', 'max_missing_run_age_ms') }} behind
+                                <template v-if="operatorRunSummaryMissingOldestStartedAt()">
+                                    (since {{ operatorRunSummaryMissingOldestStartedAt() }})
+                                </template>.
+                            </p>
                             <p>
                                 Wait rows: {{ operatorProjectionMetricLabel('run_waits', 'rows') }} rows across
                                 {{ operatorProjectionMetricLabel('run_waits', 'projected_runs') }} runs,
@@ -1065,6 +1071,32 @@ export default {
             return this.operatorProjectionMetric(group, key).toLocaleString();
         },
 
+        operatorProjectionDurationMetricLabel(group, key) {
+            const value = this.operatorProjectionMetric(group, key);
+
+            return value > 0 ? moment.duration(value).humanize() : '-';
+        },
+
+        operatorRunSummaryMissingAgeAvailable() {
+            const projections = (this.operatorMetrics && this.operatorMetrics.projections) || {};
+            const runSummaries = projections.run_summaries || {};
+
+            if (runSummaries.max_missing_run_age_ms === undefined
+                || runSummaries.max_missing_run_age_ms === null) {
+                return false;
+            }
+
+            return Number(runSummaries.missing || 0) > 0
+                || Number(runSummaries.max_missing_run_age_ms || 0) > 0;
+        },
+
+        operatorRunSummaryMissingOldestStartedAt() {
+            const projections = (this.operatorMetrics && this.operatorMetrics.projections) || {};
+            const runSummaries = projections.run_summaries || {};
+
+            return runSummaries.oldest_missing_run_started_at || null;
+        },
+
         operatorProjectionNeedsRebuild() {
             return this.operatorProjectionMetric('run_summaries', 'needs_rebuild')
                 + this.operatorProjectionMetric('run_waits', 'needs_rebuild')

tests/Feature/V2DashboardStatsControllerTest.php

@@ -903,6 +903,36 @@ public function testIndexExposesDispatchFailedAge(): void
         );
     }
 
+    public function testIndexExposesRunSummaryMissingAge(): void
+    {
+        config()->set('waterline.engine_source', 'v2');
+
+        $response = $this->get('/waterline/api/stats')->assertStatus(200);
+
+        $projections = $response->json('operator_metrics.projections');
+        $runSummaries = is_array($projections['run_summaries'] ?? null) ? $projections['run_summaries'] : null;
+
+        if (! is_array($runSummaries)
+            || ! array_key_exists('max_missing_run_age_ms', $runSummaries)
+            || ! array_key_exists('oldest_missing_run_started_at', $runSummaries)) {
+            $this->markTestSkipped(
+                'Vendored workflow package predates the run-summary projection-lag rollout-safety '
+                . 'contract (operator_metrics.projections.run_summaries.{oldest_missing_run_started_at,max_missing_run_age_ms}).',
+            );
+        }
+
+        $this->assertTrue(
+            $runSummaries['oldest_missing_run_started_at'] === null
+                || is_string($runSummaries['oldest_missing_run_started_at']),
+            'operator_metrics.projections.run_summaries.oldest_missing_run_started_at must be null or ISO-8601 string',
+        );
+        $this->assertTrue(
+            $runSummaries['max_missing_run_age_ms'] === null
+                || is_int($runSummaries['max_missing_run_age_ms']),
+            'operator_metrics.projections.run_summaries.max_missing_run_age_ms must be null or integer milliseconds',
+        );
+    }
+
     public function testIndexExposesMatchingRole(): void
     {
         config()->set('waterline.engine_source', 'v2');