Rename cli/ to unsloth_cli/ to fix namespace collision with stringzilla (#4393)

* Rename cli/ to unsloth_cli/ to fix namespace collision with stringzilla

stringzilla installs a namespace package at cli/ (cli/split.py, cli/wc.py)
in site-packages without an __init__.py. When unsloth is installed as an
editable package (pip install -e .), the entry point script does
`from cli import app` which finds stringzilla's namespace cli/ first and
fails with `ImportError: cannot import name 'app' from 'cli'`.

Non-editable installs happened to work because unsloth's cli/__init__.py
overwrites the namespace directory, but this is fragile and breaks if
stringzilla is installed after unsloth.

Renaming to unsloth_cli/ avoids the collision entirely and fixes both
editable and non-editable install paths.

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Update stale cli/ references in comments and license files

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

cli.py

@@ -1,7 +1,7 @@
 # SPDX-License-Identifier: AGPL-3.0-only
 # Copyright 2026-present the Unsloth AI Inc. team. All rights reserved. See /studio/LICENSE.AGPL-3.0
 
-from cli import app
+from unsloth_cli import app
 
 if __name__ == "__main__":
     app()