fix: Task completion result and null duration display bugs

1. task-worker.ts: Pass full result object to completeTask instead of
   non-existent result.data property (was causing {} to be stored)

2. WorkersDashboard.tsx: Handle null running_seconds in formatSecondsToTime
   (was displaying "nulls" due to JS type coercion)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/src/tasks/task-worker.ts

@@ -2249,7 +2249,7 @@ export class TaskWorker {
 
       if (result.success) {
         // Layer 1: Verify DB completion was recorded
-        const dbVerified = await taskService.completeTask(task.id, { result: result.data });
+        const dbVerified = await taskService.completeTask(task.id, result);
         if (!dbVerified) {
           console.error(`[TaskWorker] ${this.friendlyName} task ${task.id} DB COMPLETION VERIFICATION FAILED`);
           await taskService.failTask(task.id, 'DB completion verification failed');
@@ -2313,7 +2313,7 @@ export class TaskWorker {
 
       if (result.success) {
         // Use WorkerSession completion but also verify with taskService
-        await WorkerSession.completeTask(task.id, this.workerId, { result: result.data });
+        await WorkerSession.completeTask(task.id, this.workerId, result);
 
         // Verify output exists for payload-creating tasks
         const outputVerification = await taskService.verifyTaskOutput(task);

cannaiq/src/pages/WorkersDashboard.tsx

@@ -587,7 +587,8 @@ function StepBadge({ worker }: { worker: Worker }) {
 }
 
 // Format seconds to human readable duration
-function formatSecondsToTime(seconds: number): string {
+function formatSecondsToTime(seconds: number | null | undefined): string {
+  if (seconds === null || seconds === undefined) return '-';
   if (seconds < 60) return `${seconds}s`;
   const mins = Math.floor(seconds / 60);
   const secs = seconds % 60;