fix(delegate-task): align metadata with opencode core task tool

Match opencode core 'task' tool behavior for metadata consistency:

1. Model fallback: When categoryModel/task.model/resumeModel is undefined,

   fall back to parentContext.model so subagent metadata always includes

   model info. Thread parentContext into executeSyncContinuation for parity.

2. Task ID consistency: unstable-agent-task was missing taskId and

   backgroundTaskId in metadata. background_output used inconsistent

   snake_case 'task_id' vs camelCase 'taskId' elsewhere. Standardize on

   camelCase: taskId = sessionID (resume id), backgroundTaskId = bg task id.

Update text output blocks to use buildTaskMetadataBlock helper.

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/tools/delegate-task/tools.ts

@@ -162,7 +162,7 @@ export function createDelegateTask(options: DelegateTaskToolOptions): ToolDefini
         if (runInBackground) {
           return executeBackgroundContinuation(args, ctx, options, parentContext)
         }
-        return executeSyncContinuation(args, ctx, options)
+        return executeSyncContinuation(args, ctx, options, parentContext)
       }
 
       if (!args.category && !args.subagent_type) {