docs: quote pip extras install examples

[nyxst4ck]

Summary

• Quote pip install examples that include extras.

Why

• Shells such as zsh can expand unquoted bracket expressions before pip receives them.

Scope

• Files changed:
• README.md
• docs/developer/code_standard_and_dev_guide.rst
• This does not change dependencies or runtime behavior.

Testing

• git diff --check

Maintainer Fit

• Small install-command correctness fix.
• Duplicate PR search terms checked: quote pip extras, quote optional dependency, zsh pip install extras, pip extras install examples