chore: improve cmd2 maintenance path

[lphuc2250gma]

Summary:

• Add focused edge-case unit tests in tests/test_utils.py for small pure helpers in cmd2/utils.py (e.g., quote/unquote, alphabetical_sort, str_to_bool, strip_ansi handling of empty/None/whitespace inputs and mixed-quote tokens), and tighten one or two narrow type annotations where Optional/Union is currently broader than the implementation requires.
• Keep the change narrow so it is straightforward to review.

Notes:

• I kept this scoped to the relevant implementation and tests.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.53%. Comparing base (e2c061c) to head (ad67406).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1669      +/-   ##
==========================================
- Coverage   99.53%   99.53%   -0.01%     
==========================================
  Files          22       22              
  Lines        4928     4903      -25     
==========================================
- Hits         4905     4880      -25     
  Misses         23       23              

Flag	Coverage Δ
unittests	99.53% <ø> (-0.01%)	⬇️

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[tleonhardt]

For the upcoming cmd2 4.0.0 release we support Python versions 3.11 or newer.

Using the | operator with a forward-declaration string type works with Python 3.14+, but does not work with older versions of Python, hence the Union is still required for forward declaration types.