fix(download): run burst2stack off a running event loop

src/sweets/download.py

@@ -29,9 +29,11 @@
 
 from __future__ import annotations
 
+import asyncio
+from concurrent.futures import ThreadPoolExecutor
 from datetime import date, datetime
 from pathlib import Path
-from typing import Any, Literal, Optional
+from typing import Any, Callable, Literal, Optional, TypeVar
 
 from dateutil.parser import parse as parse_date
 from dolphin.workflows.config import YamlModel
@@ -43,6 +45,27 @@
 
 from ._log import log_runtime
 
+_T = TypeVar("_T")
+
+
+def _call_off_running_loop(fn: Callable[..., _T], *args: Any, **kwargs: Any) -> _T:
+    """Call `fn` even when this thread already owns a running event loop.
+
+    `burst2safe` downloads via `asyncio.run()`, which raises `RuntimeError`
+    when invoked from a thread that already has a running loop (a Jupyter or
+    IPython kernel, `jupyter execute`, etc.). In that case `fn` is run in a
+    dedicated worker thread so its `asyncio.run()` gets a fresh loop. With no
+    running loop (the normal script/CLI path) `fn` is called directly.
+    """
+    try:
+        asyncio.get_running_loop()
+    except RuntimeError:
+        return fn(*args, **kwargs)
+
+    with ThreadPoolExecutor(max_workers=1) as pool:
+        return pool.submit(fn, *args, **kwargs).result()
+
+
 FlightDirection = Literal["ASCENDING", "DESCENDING"]
 
 
@@ -225,7 +248,8 @@ def download(self) -> list[Path]:
         self.out_dir.mkdir(parents=True, exist_ok=True)
         logger.info(self.summary())
 
-        result = burst2stack(
+        result = _call_off_running_loop(
+            burst2stack,
             rel_orbit=self.track,
             start_date=self.start,
             end_date=self.end,