v2: allow sync/missing queue driver when task_dispatch_mode=poll

Backend capability reporting flagged `queue_sync_unsupported` and
`queue_connection_missing` as hard errors regardless of dispatch mode.
In poll mode tasks are delivered to workers over HTTP, so the queue
backend is unused for task delivery and a sync or missing queue
connection is a legitimate configuration.

Downgrade both codes from 'error' to 'info' when
workflows.v2.task_dispatch_mode=poll so:

- BackendCapabilities::isSupported() returns true
- /api/health reports the backend as 'ok'
- TaskBackendCapabilities::recordClaimFailureIfUnsupported() stops
  marking task claims as failed with last_claim_error=queue_sync_unsupported
- capabilities.requires_worker flips to false so clients know the queue
  worker is not a prerequisite

Queue mode behaviour is unchanged — sync/missing queues still produce
error-level issues there.

Three new BackendCapabilitiesTest cases pin the contract.

Closes #286.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: durable-workflow-ops

src/V2/Support/BackendCapabilities.php

@@ -103,19 +103,30 @@ private static function queue(?string $configuredConnection = null): array
             : self::normalize(config(sprintf('queue.connections.%s.driver', $connection)));
         $issues = [];
 
+        // In poll mode, tasks are delivered to workers via HTTP poll rather than
+        // through a Laravel queue, so a sync or missing queue driver is an
+        // acceptable configuration — the queue backend is simply unused for
+        // task delivery. We still surface an informational note so operators
+        // can see what will happen if they later flip back to queue mode.
+        $pollMode = self::normalize(config('workflows.v2.task_dispatch_mode')) === 'poll';
+
         if ($connection === null || $driver === null) {
             $issues[] = self::issue(
                 'queue',
-                'error',
+                $pollMode ? 'info' : 'error',
                 'queue_connection_missing',
-                'Workflow v2 requires a configured asynchronous queue connection for durable task delivery.',
+                $pollMode
+                    ? 'No queue connection is configured; task dispatch runs in poll mode so workers receive tasks over HTTP instead of a queue worker.'
+                    : 'Workflow v2 requires a configured asynchronous queue connection for durable task delivery.',
             );
         } elseif ($driver === 'sync') {
             $issues[] = self::issue(
                 'queue',
-                'error',
+                $pollMode ? 'info' : 'error',
                 'queue_sync_unsupported',
-                'Workflow v2 requires an asynchronous queue worker; the sync queue driver executes jobs inline and cannot provide the worker/lease boundary.',
+                $pollMode
+                    ? 'Queue driver is [sync], which is acceptable in poll mode because tasks are delivered over HTTP instead of a queue worker.'
+                    : 'Workflow v2 requires an asynchronous queue worker; the sync queue driver executes jobs inline and cannot provide the worker/lease boundary.',
             );
         }
 
@@ -126,7 +137,7 @@ private static function queue(?string $configuredConnection = null): array
             'capabilities' => [
                 'async_delivery' => $driver !== null && $driver !== 'sync',
                 'delayed_delivery' => $driver !== null && $driver !== 'sync',
-                'requires_worker' => true,
+                'requires_worker' => ! $pollMode,
                 'max_delay_seconds' => $driver === 'sqs' ? 900 : null,
                 'after_commit_option' => $connection === null ? null : config(
                     sprintf('queue.connections.%s.after_commit', $connection)

tests/Unit/V2/BackendCapabilitiesTest.php

@@ -149,4 +149,62 @@ public function testMysqlDatabaseDoesNotPublishConcurrencyNote(): void
 
         $this->assertArrayNotHasKey('concurrent_write_safety', $snapshot['structural_limits']['backend_adjustments']);
     }
+
+    // ---------------------------------------------------------------
+    //  Poll-mode queue relaxations (#286)
+    // ---------------------------------------------------------------
+
+    public function testPollModeAllowsSyncQueueDriver(): void
+    {
+        config()->set('workflows.v2.task_dispatch_mode', 'poll');
+        config()->set('queue.default', 'sync');
+        config()->set('queue.connections.sync.driver', 'sync');
+
+        $snapshot = BackendCapabilities::snapshot();
+
+        $this->assertTrue($snapshot['queue']['supported']);
+        $this->assertTrue(BackendCapabilities::isSupported($snapshot));
+        $this->assertFalse($snapshot['queue']['capabilities']['requires_worker']);
+
+        $queueIssue = collect($snapshot['issues'])
+            ->firstWhere('code', 'queue_sync_unsupported');
+
+        $this->assertNotNull($queueIssue, 'The queue_sync_unsupported note should still be recorded informationally.');
+        $this->assertSame('info', $queueIssue['severity']);
+    }
+
+    public function testPollModeAllowsMissingQueueConnection(): void
+    {
+        config()->set('workflows.v2.task_dispatch_mode', 'poll');
+        config()->set('queue.default', null);
+
+        $snapshot = BackendCapabilities::snapshot();
+
+        $this->assertTrue($snapshot['queue']['supported']);
+        $this->assertTrue(BackendCapabilities::isSupported($snapshot));
+
+        $queueIssue = collect($snapshot['issues'])
+            ->firstWhere('code', 'queue_connection_missing');
+
+        $this->assertNotNull($queueIssue);
+        $this->assertSame('info', $queueIssue['severity']);
+    }
+
+    public function testQueueModeStillRejectsSyncQueueDriver(): void
+    {
+        config()->set('workflows.v2.task_dispatch_mode', 'queue');
+        config()->set('queue.default', 'sync');
+        config()->set('queue.connections.sync.driver', 'sync');
+
+        $snapshot = BackendCapabilities::snapshot();
+
+        $this->assertFalse($snapshot['queue']['supported']);
+        $this->assertFalse(BackendCapabilities::isSupported($snapshot));
+
+        $queueIssue = collect($snapshot['issues'])
+            ->firstWhere('code', 'queue_sync_unsupported');
+
+        $this->assertNotNull($queueIssue);
+        $this->assertSame('error', $queueIssue['severity']);
+    }
 }