fix: read rest-section-adorns from the configuration file

[Eljees]

Problem

Every option is read back from the configuration file under its own hyphenated
command line name — in-place, wrap-summaries, pre-summary-space, non-cap
and the rest. --rest-section-adorns is the single exception: configuration.py
reads it as rest_section_adorns, with underscores.

docs/source/configuration.rst documents the hyphenated spelling:

The user can override this default list of characters by passing a regex from the
command line or setting the rest-section-adorns option in the configuration file.

So the spelling the documentation asks for is exactly the one that gets dropped —
silently. No error, no warning; the run just uses the default adornment regex.

Reproducer

# pyproject.toml
[tool.docformatter]
rest-section-adorns = "[!]{4,}"

>>> c = Configurater(["docformatter", "--config", "pyproject.toml", "x.py"])
>>> c.do_parse_arguments()
>>> c.flargs
{'rest-section-adorns': '[!]{4,}'}          # the file was parsed fine
>>> c.args.rest_section_adorns
'[!\\"#$%&\'()*+,-./:;<=>?@[\\]^_`{|}~]{4,}'  # ... and the value never arrives

Switching the key to rest_section_adorns in the same file makes it work, but that
spelling is not documented anywhere.

Why this looks like a typo rather than a convention

Mechanically comparing, for each add_argument block, the long option name against
the key it is read from gives one mismatch out of twenty-one:

--in-place                in-place                ok
--check                   check                   ok
...
--rest-section-adorns     rest_section_adorns     <-- mismatch
--wrap-summaries          wrap-summaries          ok
--wrap-descriptions       wrap-descriptions       ok
...

Fix

Read the documented hyphenated key first and keep the underscored one as a fallback,
so anyone who found the undocumented spelling by reading the source keeps working.

No documentation change is needed — the docs were already right.

Tests

TestRestSectionAdornsConfigKey in tests/test_configuration_functions.py, five cases:

test	before	after
test_hyphenated_key_is_honored	fails	passes
test_hyphenated_key_wins_over_underscored_key	fails	passes
test_underscored_key_is_still_honored	passes	passes
test_default_is_used_when_key_is_absent	passes	passes
test_command_line_overrides_the_configuration_file	passes	passes

The last three are controls: they are green before and after, which is what shows the
change is additive rather than a behaviour swap.

Verification

Run in a clean venv with the dependency set from [testenv] in tox.ini:

	result
master (d5c7b77), whole suite	551 passed, 3 skipped
this branch, whole suite	556 passed, 3 skipped (551 + the 5 new)
new failures against master	none
source reverted, new tests kept	2 failed / 3 passed — the two that should fail
black --check, isort --check on the changed source	clean
docformatter --check --config ./pyproject.toml on its own source	exit 0

tests/ is excluded in .pre-commit-config.yaml, so the added test block was
formatted on its own and no existing test lines are touched — the test diff is
additions only.

[Eljees]

Flagging one thing so the red check is not read as mine: Run linters on code base fails here, and it fails on master at d5c7b77 with the same three hooks and the same messages —

• fix end of files rewriting CHANGELOG.md
• pydocstyle D301 on src/docformatter/classify.py:481
• mypy [assignment] on src/docformatter/configuration.py:46

I pulled both job logs and diffed them; the failing set is identical, and this branch touches none of the three. The six test jobs (3.10 through 3.14 and pypy3.9) are green.