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/requests.py

@@ -303,6 +303,18 @@ def requests(
                     raise
 
         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_requests_complete",
@@ -310,6 +322,10 @@ def requests(
                 context={
                     "url_count": len(urls),
                     "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,
                 },
             )