Scope cleanup routines to files created by the current download

cleanup_partial_files() deleted every *.part and *.fNNN.* file in the
whole download directory, and cleanup_subtitle_files() deleted any new
.vtt/.srt under it recursively - including files belonging to other
applications (e.g. a browser's own .part downloads in ~/Downloads).

Track every destination path yt-dlp reports for this download and
restrict both cleanup passes to those files and their .part/.ytdl
siblings.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

ytsage/core/ytsage_downloader.py

@@ -112,18 +112,23 @@ class DownloadThread(QThread):
         self.last_file_path: Optional[str] = None  # Initialize full file path storage
         self.subtitle_files: List[str] = []  # Track subtitle files that are created
         self.initial_subtitle_files: Set[Path] = set()  # Track initial subtitle files before download
+        self.download_files: Set[Path] = set()  # Every destination path this download wrote to
 
     def cleanup_partial_files(self) -> None:
-        """Delete any partial files including .part and unmerged format-specific files"""
+        """Delete partial files (.part/.ytdl and unmerged .fNNN. streams), but only
+        those belonging to destinations this download actually wrote — the download
+        directory may contain unrelated files from other applications."""
         try:
             pattern = re.compile(r"\.f\d+\.")  # Pattern to match format codes like .f243.
-            for file_path in self.path.iterdir():
-                if file_path.suffix == ".part" or pattern.search(file_path.name):
-                    self._safe_delete_with_retry(file_path)
+            for dest in self.download_files:
+                candidates = [dest.with_name(dest.name + ".part"), dest.with_name(dest.name + ".ytdl")]
+                if dest.suffix == ".part" or pattern.search(dest.name):
+                    candidates.append(dest)
+                for file_path in candidates:
+                    if file_path.exists():
+                        self._safe_delete_with_retry(file_path)
         except Exception as e:
             logger.exception(f"Error cleaning partial files: {e}")
-            # Don't emit error signal for cleanup issues to avoid crashing the thread
-            logger.error(f"Error cleaning partial files: {e}")
 
     def _safe_delete_with_retry(self, file_path: Path, max_retries: int = 5, delay: float = 2.0) -> None:
         """Safely delete a file with retry mechanism for file locking issues across platforms"""
@@ -219,8 +224,15 @@ class DownloadThread(QThread):
                 logger.debug(f"Deleted {deleted_count[0]} of {len(self.subtitle_files)} tracked subtitle files")
 
             # --- Method 2: Delete new subtitle files not in initial set ---
+            # Only touch subtitles belonging to files this download wrote; the
+            # directory may contain subtitle files from other processes.
+            download_stems = {p.stem for p in self.download_files} | {Path(f).stem for f in self.subtitle_files or []}
             new_subtitle_files: Set[Path] = {
-                f for f in Path(self.path).rglob("*") if f.suffix in [".vtt", ".srt"] and f not in self.initial_subtitle_files
+                f
+                for f in Path(self.path).rglob("*")
+                if f.suffix in [".vtt", ".srt"]
+                and f not in self.initial_subtitle_files
+                and any(f.name.startswith(stem) for stem in download_stems if stem)
             }
             for subtitle_file in new_subtitle_files:
                 deleted_count[1] += safe_delete(path=subtitle_file)
@@ -619,6 +631,7 @@ class DownloadThread(QThread):
                 filepath = dest_match.group(1).strip()
                 self.current_filename = Path(filepath).name
                 self.last_file_path = filepath  # Store the full path for later cleanup
+                self.download_files.add(Path(filepath))
                 logger.debug(f"Extracted filename: {self.current_filename}")  # DEBUG
 
                 # Check if this is an audio-only download by looking in the previous lines
@@ -711,6 +724,7 @@ class DownloadThread(QThread):
                 dest_path = match.group(1).strip()
                 self.current_filename = Path(dest_path).name
                 self.last_file_path = dest_path
+                self.download_files.add(Path(dest_path))
                 logger.debug(f"Captured destination filename: {self.current_filename}")
         elif "Downloading API JSON" in line:
             self.status_signal.emit(_("download.processing_playlist"))
@@ -771,6 +785,7 @@ class DownloadThread(QThread):
                 merged_filepath = merger_match.group(1).strip()
                 self.current_filename = Path(merged_filepath).name
                 self.last_file_path = merged_filepath
+                self.download_files.add(Path(merged_filepath))
                 logger.debug(f"Updated to merged filename: {self.current_filename}")
         elif "SponsorBlock" in line:
             self.status_signal.emit(_("download.removing_sponsor_segments"))