Fix video I/O: context manager, no-audio guard, temp cleanup (#483)

* Fix video I/O: context manager, no-audio guard, temp cleanup

Addresses PR #482 review comments:
- Use `with av.open()` context manager (proper resource cleanup)
- Guard against videos with no audio track (was IndexError)
- Clean up temp directory with shutil.rmtree in finally block
- Skip videos without audio instead of crashing

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* Use TemporaryDirectory context manager instead of mkdtemp

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* Fix fragile path calculation and empty audio list crash

- Use os.path.relpath instead of str.replace for safe relative paths
  (leading slash caused writes to root directory)
- Return empty dict when no audio tracks found instead of crashing
  read_files_from_disk with empty list

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: satra

src/senselab/video/tasks/input_output.py

@@ -9,7 +9,7 @@
 import numpy as np
 import soundfile as sf
 
-from senselab.utils.data_structures import from_strings_to_files, get_common_directory
+from senselab.utils.data_structures import from_strings_to_files, get_common_directory, logger
 from senselab.utils.tasks.input_output import read_files_from_disk
 
 
@@ -33,22 +33,29 @@ def extract_audios_from_local_videos(
         A dataset dict of the extracted audio files.
     """
 
-    def _extract_audio_from_local_video(video_path: Path, output_audio_path: str, fmt: str, codec: str) -> None:
-        """Extract audio from a video file using PyAV."""
-        container = av.open(str(video_path))
-        audio_stream = container.streams.audio[0]
-        sample_rate = audio_stream.rate or 16000
+    def _extract_audio_from_local_video(video_path: Path, output_audio_path: str, fmt: str, codec: str) -> bool:
+        """Extract audio from a video file using PyAV.
 
-        frames = []
-        for frame in container.decode(audio=0):
-            arr = frame.to_ndarray()
-            if arr.ndim > 1:
-                arr = arr.mean(axis=0)  # downmix to mono
-            frames.append(arr)
-        container.close()
+        Returns:
+            True if audio was extracted, False if the video has no audio track.
+        """
+        with av.open(str(video_path)) as container:
+            if not container.streams.audio:
+                logger.warning("No audio track found in %s, skipping.", video_path)
+                return False
+
+            audio_stream = container.streams.audio[0]
+            sample_rate = audio_stream.rate or 16000
+
+            frames = []
+            for frame in container.decode(audio=0):
+                arr = frame.to_ndarray()
+                if arr.ndim > 1:
+                    arr = arr.mean(axis=0)  # downmix to mono
+                frames.append(arr)
 
         if not frames:
-            return
+            return False
 
         audio_data = np.concatenate(frames)
 
@@ -61,20 +68,21 @@ def _extract_audio_from_local_video(video_path: Path, output_audio_path: str, fm
             )
 
         sf.write(output_audio_path, audio_data, sample_rate, format=fmt.upper())
+        return True
 
     if isinstance(files, str):
         files = [files]
     formatted_files = from_strings_to_files(files)
     common_path = get_common_directory(files)
 
-    temp_dir = tempfile.mkdtemp()
-
-    audio_files_paths = []
-    for file in formatted_files:
-        base_file_name = os.path.splitext(str(file.filepath).replace(common_path, ""))[0]
-        output_audio_path = os.path.join(temp_dir, f"{base_file_name}.{audio_format}")
-        os.makedirs(os.path.dirname(output_audio_path), exist_ok=True)
-        _extract_audio_from_local_video(file.filepath, output_audio_path, fmt=audio_format, codec=acodec)
-        audio_files_paths.append(output_audio_path)
-
-    return read_files_from_disk(audio_files_paths)
+    with tempfile.TemporaryDirectory(prefix="senselab-video-io-") as temp_dir:
+        audio_files_paths = []
+        for file in formatted_files:
+            rel_path = os.path.relpath(file.filepath, common_path)
+            base_file_name = os.path.splitext(rel_path)[0]
+            output_audio_path = os.path.join(temp_dir, f"{base_file_name}.{audio_format}")
+            os.makedirs(os.path.dirname(output_audio_path), exist_ok=True)
+            if _extract_audio_from_local_video(file.filepath, output_audio_path, fmt=audio_format, codec=acodec):
+                audio_files_paths.append(output_audio_path)
+
+        return read_files_from_disk(audio_files_paths) if audio_files_paths else {}