docs(tests): second pass over tests outside tests/protocols (#1103)

[JarryShaw]

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• 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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Summary

#1103 round 2: the files phase 1 left unread, plus the phase-1 reviewers' follow-ups.

Prose only: ASTs match the base once docstrings are blanked.

• CI reach: engine-tests no longer collects tests/vendor or
  tests/project (ci: rebuild engine-tests as a Python × engine matrix with three cell outcomes #849); the test extra carries requests and bs4
  (IPX vendor crawler is doubly broken: Wikipedia 403s the default User-Agent, and the socket-number table is gone #507); bs4[html5lib] ships in vendor and dev, not all;
  experimental.yml runs pytest too; five workflows install .[all].
• Public API: dropping 'vendor' from EXCLUDED_ROOTS fails for
  pcapkit.vendor and pcapkit.vendor.ipx, tracked in fix(vendor): __all__ gaps keep pcapkit.vendor out of the public-API sweep #1772.
• Retired behaviour stated as current: the tracebacklimit side effect
  (fix(utilities): stop truncating every traceback for a loud BaseError #983), minting by Method, AppType and OptionType (const: bring the 16 bespoke registries onto EnumRegistry, after fixing the base's str-key dispatch #860, fix(const,vendor): bring the AppType family onto EnumRegistry, stop it minting (#860) #874),
  TransportProtocol as an IntFlag (reg: drop TransportProtocol's IntFlag base once nothing builds a composite #808), AppType.get(name) never matches an existing member and silently mints a port=-1 member instead #734 as open.
• Counts dropped or anchored: proto entries, cyclic-import
  findings, 116 of 117 (fix(vendor): make the handover_initiate_status crawler reachable (release blocker for make vendor) #531), the ci(release): a push that releases nothing leaves 10 red conda checks on main while 1.5.0b12 is unfinished (#1634) #1748 mutation rows, module,
  workflow and call-site totals.
• References: Method.get's callers, renamed test ids, RFC 959
  section 5.3, a gate cited by line number, "this PR" as fix(const,vendor): bring the AppType family onto EnumRegistry, stop it minting (#860) #874,
  "this branch" as a main commit from before refactor(corekit): house all four sentinels in one shared module (#911) #922.

Refs #1103

[JarryShaw]

Verdict: GOOD TO GO at 433c825f4. Sonnet review and re-check (author: Opus). The first review blocked on the #922 base commit in test_sentinels_housing_unit.py:23. The docstring now says "a main commit from before #922", checked against the PR's base. Stacked on #1788. The AST guard is identical against the base, tests/project passes, and every added directive says 1.5.0.

[JarryShaw]

Conflicts with #1779 in tests/project/test_public_api.py and tests/vendor/test_crawler_reachability_unit.py; whichever merges second, I rebase.

[JarryShaw]

Verdict: GOOD TO GO at dbd32829a. This is 433c825f4 rebased from #1788's branch onto main, with an identical range-diff and patch-id. After the fix round the two PRs share no files, so this one is no longer stacked; it now targets main and gets CI. The earlier verdict carries over.