[vshalpnjabi]

Description

python -m spacy download fails with exit 2 in a uv-created venv that isn't
activated. When pip isn't available, _get_pip_install_cmd() falls back to
["uv", "pip", "install"] with no --python, so uv can't find the
environment ("No virtual environment found").

This passes --python sys.executable so uv installs into the running
interpreter, the same target the pip branch uses (sys.executable -m pip).
Activated venvs still work, since --python takes precedence over
VIRTUAL_ENV.

Fixes #14055

Tested on Linux, Python 3.12.3, uv 0.13.6:

• Before: spaCy 3.8.18 in an unactivated uv venv,
  cd / && env -u VIRTUAL_ENV /tmp/v/bin/python -m spacy download en_core_web_sm
  exits 2 with "No virtual environment found".
• After: the same command with this branch installs en_core_web_sm 3.8.0.
• python -m pytest spacy/tests/test_cli.py: 121 passed, 4 skipped.
• ruff check and ruff format --check on the touched files.

Types of change

Bug fix

Checklist

• I confirm that I have the right to submit this contribution under the project's MIT license.
• I ran the tests, and all new and existing tests passed.
• My changes don't require a change to the documentation, or if they do, I've added all required information.