docs(tests): fourth whole-repo pass over tests (#1103)

[JarryShaw]

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• Followed the coding style (make pylint, make mypy, make isort)

• make test passes, and a test case covers the change. Narrow runs only, listed below.

• Added a changelog entry under docs/source/changelog/ and regenerated CHANGELOG.md, if the change is user-visible: N/A — centralised in docs(changelog): shared 1.5.0 changelog — long-lived, merges last (#610, #616, #617, #618, #620) #657

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Tick the commit type your subject line carries.

• fix — corrects a defect
• feat — adds a feature
• perf — changes performance, not behaviour
• refactor — changes neither behaviour nor performance
• test — tests only
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The fourth whole-repo prose pass of #1103, over test prose. It changes prose only: every changed .py file's AST is unchanged once string expressions are blanked, except where a docstring is added or vendor template text is edited together with its generated const file.

Accuracy:

• correct the pyproject.toml lines the linktype-209 gate cites, and say
  that cron-vendor.yml does run that pin when a crawl changes a constant
• the MH default-argument cleanup comment no longer calls missing loud
  or says it sets sys.tracebacklimit (design(const): get(value, default) on an out-of-range value returns the default but logs a CRITICAL error and installs pcapkit's excepthook #1845)
• the builtin-parity rationale accounts for get()'s _CaughtByCaller block
• conftest.py's docstring lists the session hooks it holds
• the PyPCAPFile marker note names the legs by version, PyPy included
• fix a "below" that pointed at a constant defined above it

Counts:

• reword codebase counts count-free in comments and docstrings, including
  the enum no-mint narrative and the arithmetic comment that no longer
  added up; the asserted constants carry the figures instead

Timed context:

• drop "today", "currently" and "as of " where they added nothing

Prose only: an AST guard with docstrings blanked is identical on every file.

Refs #1103

[JarryShaw]

NEEDS CHANGES at cd2c8f42e. In tests/const/test_const_linktype_209_unit.py, the pyproject.toml range stops mid-sentence; it should be :325-332. In tests/protocols/internet/test_mh_unit.py, the _drop_tracebacklimit comment adds "any more". The touched hunks also keep a few counts and some timed context ("the eight", "now reaches", "any more") in test_ipv6_ext_unit.py, test_fields_copy_dispatch_unit.py and test_const_enum_no_mint.py; drop them.

[JarryShaw]

NEEDS CHANGES at aa5127de8. The three requested fixes are done, and every changed .py is still AST-identical to main. One rewrite now loses a fact. In tests/const/test_const_enum_no_mint.py:50, #860 step 2's PR 1 converted every one of those classes except AppType, which PR 2 converted later (see line ~107). "most" hides that, so name the exception rather than count it. Also drop "any more" from the comment at ~1488, in the same RulingConversionSourceTests block where the other one was removed.

[JarryShaw]

GOOD TO GO at 1ce9933e4. "Every one of those classes except AppType" checks out: the eight others are in BESPOKE_UNMINT_CONVERTED_REGISTRIES or covered by BespokeOpenVocabularyUnmintConvertedTests, PR 2 converted AppType, and CGAType is correctly outside the set. The comment block's claims hold on import. The file is AST-identical to main, and test_const_enum_no_mint.py passes.

[github-actions]

Coverage: 90.07% (unit tier, Python 3.15, 1ce9933e4, Unit Tests run success)

Package	Statements	Missed	Branches	Partial	Cover
pcapkit (top level)	104	2	20	2	96.77%
pcapkit/const	19595	881	2618	867	92.11%
pcapkit/corekit	2504	70	792	36	96.54%
pcapkit/dumpkit	276	3	100	3	98.40%
pcapkit/foundation	2916	164	1016	34	93.59%
pcapkit/interface	138	7	52	5	93.68%
pcapkit/protocols	17411	224	4580	189	98.10%
pcapkit/toolkit	872	177	298	8	77.18%
pcapkit/utilities	522	2	158	4	99.12%
pcapkit/vendor	4431	2341	1018	156	43.64%

Per-file detail: the coverage-html artifact of this run.