Fix launcher option replacement guard

[huangminghuang]

Summary

Fix TestHarness launcher option replacement when an option is followed by another option instead of a value.

What changed

• Add _is_command_option() to identify command-line option tokens.
• Guard option-value removal with a bounds check and only remove the next token when it is actually a value.

Why

The port-sharded test changes in PR #369 rely on overriding generated nodeop arguments. The existing replacement logic can treat the following --option as a value and remove it, or read past the end of the command list.

Testing

• python3 -m py_compile tests/TestHarness/launcher.py
• git diff --check

Notes

• This PR is stacked on PR Enable port-sharded concurrent NP and LR tests #369: Enable port-sharded concurrent NP and LR tests #369