Fix type-check failures with ty 0.0.87

[DG-Elom]

ty 0.0.87 (released 2026-10-13 23:06 UTC) reports 3 new diagnostics on main, so the type-check jobs now fail on every PR (e.g. #1773):

error[invalid-mutable-override]: Invalid override of attribute `formatter_class`
   --> cmd2/argparse_utils.py:771:9
error[invalid-attribute-override]: Invalid override of attribute `description`
   --> cmd2/argparse_utils.py:772:9
error[invalid-attribute-override]: Invalid override of attribute `epilog`
   --> cmd2/argparse_utils.py:773:9

These are the intentional re-declarations for rich-argparse that already carry # type: ignore[assignment] for mypy, so this adds the matching # ty: ignore[...] comments, following the existing # type: ignore[...] # ty: ignore[...] convention in this file.

Checked locally on top of main with ty 0.0.87: ty check passes, mypy reports no issues, and ruff check/format are clean.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.75%. Comparing base (01a52e8) to head (e3789ef).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1774   +/-   ##
=======================================
  Coverage   99.75%   99.75%           
=======================================
  Files          23       23           
  Lines        6473     6473           
=======================================
  Hits         6457     6457           
  Misses         16       16           

Flag	Coverage Δ
unittests	99.75% <100.00%> (ø)

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