docs(tests): correct stale claims in test docstrings and comments (#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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Description

Part of #1103, the whole-repository prose sweep, for the tests slice. It follows the #719 rules: prose only, accuracy first, no churn and no timed context.

Prose only: the AST of every changed module, string expression
statements blanked, is identical to origin/main's.

• Timed context: "this PR" names its PR (ci: add a per-engine test job for Scapy, PyShark, PyPCAPFile and pcap-ct #755, fix(http): check the buffer's length, not just the declared one, in HTTP/2's frame guard #802, fix(reg)!: drop TransportProtocol's IntFlag base now that nothing composes #836, fix(vendor): make the LinkType legacy-sink rule value-aware #854,
  fix(const,vendor): bring 8 bespoke registries onto EnumRegistry, stop them minting #869, fix(const,vendor): bring the AppType family onto EnumRegistry, stop it minting (#860) #874, refactor(corekit): house all four sentinels in one shared module (#911) #922, fix(vendor): source ExtensionHeader from the extension-header registry, not the protocol-numbers flag (#925) #926); "today", "as of writing", "right now",
  "until now" and a "now installs" are anchored or dropped.
• Stale state: closed issues no longer read as open or in flight
  (_make_mptcp_*/_read_mptcp_* length arithmetic is wrong at six more sites beyond MP_CAPABLE #576, HIP parameter padding aligns the contents, not the record, so every parameter pcapkit emits is 4 (mod 8) octets #651/fix(hip): pad HIP parameters to the record length RFC 7401 gives, not the contents (#651) #664, tests/_support.py leaves bare stub modules in sys.modules, so tests/corekit + tests/project in one process fails three test_public_api tests #674, fix(protocols): repair __all__ entries that name nothing, and guard the class #527, fix(vendor): make the handover_initiate_status crawler reachable (release blocker for make vendor) #531), and the minting, KNOWN_DEFECTS,
  vendor-depth and MPTCP-parse narratives are put in the past tense
  where later changes retired them.
• Moved or renamed names: beholder's home, HTTP._read_http_header,
  PCAPNGSectionRuleTests, test_new_engine_parity_runtime, and the
  scapy cast that fix(toolkit): scapy reads IP and TCP only in layers the default engine dissects (#1635, #1636) #1652 removed.
• Line references: about 50 file:line pointers into pcapkit/,
  pyproject.toml, Pipfile and sibling tests re-measured.
• Counts re-derived: raise targets and nested defs in
  test_docstring_contract, and the four returned nested defs it names.
• A pytest-subtests claim corrected to pytest's own reporting.

Checks:

• An AST guard holds on every changed .py: code is identical once docstrings are blanked.
• tests/project and every test that reads the edited paths pass.
• A merged Sphinx build of all nine slices adds no new warnings.
• A Sonnet cross-review returned GOOD TO GO.

Not covered here; a round-2 PR follows: function, method and class docstrings and inline comments (about 2.3 MB), starting with the largest files.

Refs #1103

[JarryShaw]

Verdict: GOOD TO GO at 4db995523. A Sonnet cross-review checked it (author: Opus).

• Scope and AST guard: 50 files, all under tests/. All 50 are identical once docstrings are blanked, and the check catches a changed literal while ignoring a changed docstring. No assertion, name or fixture changed.
• Accuracy: every hunk was read and about 65 claims were checked, with 0 wrong claims and 0 churn. The 24 swaps from "this PR" to #N each match the git blame PR of the original line.
• Non-blocking, for round 2:
  • test_public_api.py:129-138 understates what dropping vendor from EXCLUDED_ROOTS takes: 2 tests fail when it is dropped;
  • a "116 of 117" figure should be anchored to fix(vendor): make the handover_initiate_status crawler reachable (release blocker for make vendor) #531;
  • one _read_http_header reference is indirect;
  • the function- and method-level docstrings have not been read yet.