[fly1d]

PtyProcess.spawn accepts a list or tuple, but slicing a tuple leaves it immutable. Replacing argv[0] with the resolved executable then raises TypeError before the child starts. Copy the accepted arguments to a list without changing the caller's input.

The regressions run real Python children through both PtyProcess and PtyProcessUnicode, checking PATH resolution, arguments with spaces, output, exit status and unchanged list/tuple inputs.

Validation on Python 3.14.7/macOS arm64:

• The identical four regression cases give two tuple failures and two passing list controls on the original code; all four pass here within the full suite.
• Full python -m pytest --timeout 60 -v: 19 passed, none skipped.
• python -m compileall -q ptyprocess tests/test_spawn.py and git diff --check pass.

Other Python versions and platforms were not tested.