feat(debug): add JSONL debug logging to decryption, muxing, and all downloaders

Expand debug logging coverage for better diagnostics when investigating download/decryption issues like QUICKTIME/cbcs problem.

unshackle/core/downloaders/aria2c.py

@@ -441,6 +441,37 @@ def download(
                 yield dict(downloaded=f"{filesize.decimal(dl_speed)}/s")
 
             time.sleep(1)
+
+        if debug_logger:
+            output_files = []
+            output_total_size = 0
+            if output_dir.exists():
+                try:
+                    for f in sorted(output_dir.iterdir()):
+                        if f.is_file():
+                            fsize = f.stat().st_size
+                            output_files.append(f.name)
+                            output_total_size += fsize
+                except OSError:
+                    output_files = ["<error listing files>"]
+
+            debug_logger.log(
+                level="DEBUG",
+                operation="downloader_aria2c_complete",
+                message="Aria2c download completed successfully",
+                context={
+                    "url_count": len(urls),
+                    "gid_count": len(gids),
+                    "completed_count": len(completed),
+                    "output_dir": str(output_dir),
+                    "output_dir_exists": output_dir.exists(),
+                    "output_files_count": len(output_files),
+                    "output_files": output_files[:10],
+                    "output_total_size": output_total_size,
+                    "filename": filename,
+                },
+            )
+
     except KeyboardInterrupt:
         DOWNLOAD_CANCELLED.set()
         raise