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

[JarryShaw]

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• You will be asked some questions, please read them carefully and answer honestly

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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
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The fourth whole-repo prose pass of #1103, over the internet protocols. 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.

Rendering:

• Drop the duplicated RPL, MPL and DFF flag stubs on the HOPOPT and
  IPv6-Opts pages, and the type prefixes on the registry comments that
  rendered a second, unlinked Type field.
• Point load_cryptography at InvalidTag rather than an unresolved module.

Reachability:

• Carry the IPv6-Ext length rules, entry paths and overrun guard on its
  page, and point the docstrings at those sections rather than at the
  unrendered module docstring; likewise ESP's algorithm support.
• List the per-suite ESP parameters the support tables left out.

Accuracy:

• Rebuild the IPv6-Ext exception table so its rows render, and title the
  page IPv6-Ext after the alias.
• Say ESP's next is None only while its payload stays opaque.
• Fill the blank IPv4 and ESP table cells, describe HIP's fixed bits as
  bits, and correct the PDM field acronyms.
• Drop the directive on beta-only PMIPv6Timestamp and the page-level copy
  of NTPTimestamp's, which its class docstring already renders.

Wording: "the extractor", "construction arguments", "see" for "c.f.", and
spec totals worded count-free.

Refs #1103

[JarryShaw]

NEEDS CHANGES at 8429f9544. Restore two counts the PR dropped: RFC 2675 §3 lists four Jumbo errors (schema/internet/ipv6.py jumbogram_error) and RFC 6705 §10.2 defines three status values (schema/internet/mh.py). Both are spec quantities, which the no-count rule exempts. The rest checked out, including the ESP tables against CIPHER_SUITES/INTEGRITY_SUITES, the AST guard and the docs gates.

[JarryShaw]

GOOD TO GO at 7a01c86c0. A Sonnet re-review checked both restored counts against the RFC text: four errors in RFC 2675 §3 and three status values in RFC 6705 §10.2. It found no other spec count dropped across the diff, and all 21 changed .py are AST-identical once docstrings are blanked.

[github-actions]

Coverage: 90.07% (unit tier, Python 3.15, 7a01c86c0, 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.