Surface ready-due queue-latency age on dw system:operator-metrics

Extends the CLI Tasks section of `dw system:operator-metrics` to
render `operator_metrics.tasks.max_ready_due_age_ms` and
`oldest_ready_due_at` when the workflow engine exposes them,
mirroring the stuck-lease-age rendering already added alongside
the transport-failure roll-up. The CLI output schema at
schemas/output/operator-metrics.schema.json now pins both keys
under `tasks` so downstream consumers of `--json` have a stable
contract for the queue-latency duration signal.

Author: durable-workflow-ops

schemas/output/operator-metrics.schema.json

@@ -32,6 +32,8 @@
             "lease_expired": { "type": ["integer", "null"] },
             "oldest_lease_expired_at": { "type": ["string", "null"] },
             "max_lease_expired_age_ms": { "type": ["integer", "null"] },
+            "oldest_ready_due_at": { "type": ["string", "null"] },
+            "max_ready_due_age_ms": { "type": ["integer", "null"] },
             "unhealthy": { "type": ["integer", "null"] }
           },
           "additionalProperties": true

src/Commands/SystemCommand/OperatorMetricsCommand.php

@@ -127,6 +127,15 @@ private function renderTasks(OutputInterface $output, array $tasks): void
         if (is_string($tasks['oldest_lease_expired_at'] ?? null)) {
             $output->writeln(sprintf('  Oldest lease expired at:  %s', $tasks['oldest_lease_expired_at']));
         }
+        if (array_key_exists('max_ready_due_age_ms', $tasks)) {
+            $output->writeln(sprintf(
+                '  Oldest ready-due age:     %d ms',
+                (int) ($tasks['max_ready_due_age_ms'] ?? 0),
+            ));
+        }
+        if (is_string($tasks['oldest_ready_due_at'] ?? null)) {
+            $output->writeln(sprintf('  Oldest ready-due at:      %s', $tasks['oldest_ready_due_at']));
+        }
         $output->writeln('');
     }
 

tests/Commands/SystemCommandTest.php

@@ -515,6 +515,8 @@ public function test_operator_metrics_command_renders_rollout_safety_signals():
         );
         self::assertStringContainsString('Oldest lease-expired age: 95000 ms', $display);
         self::assertStringContainsString('Oldest lease expired at:  2026-04-24T11:28:25Z', $display);
+        self::assertStringContainsString('Oldest ready-due age:     15000 ms', $display);
+        self::assertStringContainsString('Oldest ready-due at:      2026-04-24T11:29:45Z', $display);
 
         self::assertStringContainsString('Runnable tasks:       7', $display);
         self::assertStringContainsString('Delayed tasks:        3', $display);
@@ -618,6 +620,20 @@ public function test_operator_metrics_schema_pins_stuck_lease_age_keys(): void
         self::assertSame(['integer', 'null'], $tasks['max_lease_expired_age_ms']['type']);
     }
 
+    public function test_operator_metrics_schema_pins_ready_due_age_keys(): void
+    {
+        $schema = json_decode(
+            (string) file_get_contents(__DIR__.'/../../schemas/output/operator-metrics.schema.json'),
+            true,
+            flags: JSON_THROW_ON_ERROR,
+        );
+
+        $tasks = $schema['properties']['operator_metrics']['properties']['tasks']['properties'];
+
+        self::assertSame(['string', 'null'], $tasks['oldest_ready_due_at']['type']);
+        self::assertSame(['integer', 'null'], $tasks['max_ready_due_age_ms']['type']);
+    }
+
     public function test_operator_metrics_command_tolerates_minimal_payload(): void
     {
         $command = new OperatorMetricsCommand();
@@ -659,6 +675,8 @@ private static function operatorMetricsPayload(): array
                     'lease_expired' => 2,
                     'oldest_lease_expired_at' => '2026-04-24T11:28:25Z',
                     'max_lease_expired_age_ms' => 95000,
+                    'oldest_ready_due_at' => '2026-04-24T11:29:45Z',
+                    'max_ready_due_age_ms' => 15000,
                     'unhealthy' => 11,
                 ],
                 'backlog' => [