[rioyu123]

python script.py puts the script's directory first on sys.path, so it can import modules that sit next to it. python -m nvtx script.py uses runpy.run_path, which does not do this for a file path. A sibling import can therefore fail with ModuleNotFoundError or pick up a different module from the current directory.

This change adds the script's absolute directory to the front of sys.path before execution, following the standard library's cProfile and profile command-line tools. It leaves argument parsing and profiling behavior unchanged.

Testing:

• Two real-subprocess regressions cover absolute and relative script paths. A conflicting module in the working directory verifies that the script's own sibling takes precedence.
• Linux, CPython 3.12: the full Python suite passes with and without --enable-injection (4,469 passed in each run).
• Windows, macOS, and other Python versions were not tested locally.

Related: #181 fixes argument forwarding, not import paths. Both changes touch the CLI and add test_main.py, so whichever merges second may need a small rebase. This PR does not include #181's changes.