Fix platform worker task not appearing in list

Two root causes:
1. Task was created in memory but not broadcast to frontend until the first
   update_task() call. If an exception happened before that, the task was
   invisible forever. Fix: broadcast immediately after task creation.
2. run_in_executor had no try/except — any exception was silently swallowed
   by asyncio.create_task with no log. Fix: wrap in try/except/finally,
   log exception via logger.exception, mark task as error.
Also: get_event_loop() → get_running_loop() (correct API for async context).

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

web_app.py

@@ -694,36 +694,41 @@ class VSRTaskWorker:
         cache_path = url_to_cache_path(video_url)
         cached = cache_path.exists()
 
+        new_task = {
+            "id": task_id,
+            "url": video_url,
+            "is_cache_file": False,
+            "cache_path": str(cache_path),
+            "inpaint_mode": ptask.get("inpaint_mode", "sttn-auto"),
+            "subtitle_areas": ptask.get("subtitle_areas", []),
+            "preview_mode": ptask.get("preview_mode", False),
+            "detect_mode": ptask.get("detect_mode", "text"),
+            "status": "pending",
+            "progress": 0,
+            "phase": "pending",
+            "detect_pct": 0, "process_pct": 0, "merge_pct": 0,
+            "download_progress": 0,
+            "cached": cached,
+            "output_path": None,
+            "error": None,
+            "platform_task_id": platform_task_id,
+            "logs": [],
+            "created_at": time.time(),
+            "started_at": None,
+            "completed_at": None,
+        }
         with task_lock:
-            tasks[task_id] = {
-                "id": task_id,
-                "url": video_url,
-                "is_cache_file": False,
-                "cache_path": str(cache_path),
-                "inpaint_mode": ptask.get("inpaint_mode", "sttn-auto"),
-                "subtitle_areas": ptask.get("subtitle_areas", []),
-                "preview_mode": ptask.get("preview_mode", False),
-                "detect_mode": ptask.get("detect_mode", "text"),
-                "status": "pending",
-                "progress": 0,
-                "phase": "pending",
-                "detect_pct": 0, "process_pct": 0, "merge_pct": 0,
-                "download_progress": 0,
-                "cached": cached,
-                "output_path": None,
-                "error": None,
-                "platform_task_id": platform_task_id,
-                "logs": [],
-                "created_at": time.time(),
-                "started_at": None,
-                "completed_at": None,
-            }
+            tasks[task_id] = new_task
+
+        # 立即广播给前端，使任务出现在列表中
+        _save_task_to_db(new_task)
+        _push(_broadcast({"type": "task_update", "task": _task_snapshot(new_task)}))
 
         # 在线程中同步执行任务
         def _do():
             _run_task(task_id)
 
-        loop = asyncio.get_event_loop()
+        loop = asyncio.get_running_loop()
 
         # 进度上报后台 loop
         async def _progress_reporter():
@@ -742,8 +747,13 @@ class VSRTaskWorker:
                     break
 
         reporter = asyncio.create_task(_progress_reporter())
-        await loop.run_in_executor(None, _do)
-        reporter.cancel()
+        try:
+            await loop.run_in_executor(None, _do)
+        except Exception:
+            logger.exception(f"[vsr_worker] 任务 #{platform_task_id} 执行异常")
+            update_task(task_id, status="error", error="worker 执行异常，详见 Worker 日志")
+        finally:
+            reporter.cancel()
 
         with task_lock:
             final = tasks.get(task_id, {})