fix(examples): use os.path.join for object_detection.py path in llm_op (#1837)

The __main__ block of `examples/python-operator-dataflow/llm_op.py`
(a developer-mode entry point for exercising the operator directly,
distinct from the operator import path used by the dora dataflow)
built a path via string concatenation:

    path = current_directory + "object_detection.py"

This produces `<dir>object_detection.py` with no separator, so
`python llm_op.py` would always fail to open the file unless it
happened to be in a directory whose name ended in a path separator.

Rescue of #1389 (RithamSharma) which identified the bug and the
correct fix (os.path.join). Reimplemented with PEP 8 spacing and
without the trailing debug comment so the example stays clean.

Co-authored-by: RithamSharma <RithamSharma@users.noreply.github.com>
Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: 3 people

examples/python-operator-dataflow/llm_op.py

@@ -299,7 +299,7 @@ def ask_llm(self, prompt):
     # Directory of the current file
     current_directory = os.path.dirname(current_file_path)
 
-    path = current_directory + "object_detection.py"
+    path = os.path.join(current_directory, "object_detection.py")
     with open(path, encoding="utf8") as f:
         raw = f.read()