docs(protocols): second-round pass over the data-model prose (#719)

[JarryShaw]

• Searched for similar pull requests
• Followed the coding style — lint not run; no code changed (AST guard below)
• make test passes, and a test case covers the change — full suite not run; affected modules run one per process, all pass
• Added a changelog entry — N/A — centralised in docs(changelog): shared 1.5.0 changelog — long-lived, merges last (#610, #616, #617, #618, #620) #657

What is the purpose of your pull request?

• docs — documentation only

---

Description

Round-two re-read of every file under pcapkit/protocols/data/ for #719 (38 files read, 14 changed). Comments and docstrings only.

• preserved keyword → reserved keyword (IPv4 ToSField/TROption, IPv6).
• HIP SolutionParameter.reserved: replaced the "used to be read as a Lifetime" history with the standing reason (only PUZZLE has a Lifetime; 0x00 would not re-serialise, per _make_puzzle_lifetime).
• NoPayload comment: Info generates __init__(self, dict_=None, **kwargs) for an annotation-less class (probed), rather than "skipping" it.
• IPv6_Ext.protocol: None also when alias is not given (read only resolves a non-None alias).
• Added doc comments for undocumented IPv4.options (set only when hdr_len > 20) and TROption.originator; fixed #:Flags. / # :Flags. on IPDFFOption.flags (the latter was not a doc comment at all).
• VLAN index comments name both 802.1Q and 802.1ad, matching vlan.py.
• Typos: crytographic, moddel, modelf, compability, Publick, Sendder, ZigBEE.

Sphinx -n, fresh dirs: 46 warnings mention this slice on both main and branch, none new. Tests (one module per process) and tests/project pass.

AST guard (every bare-string Expr stripped), origin/main vs branch:

File	Identical
pcapkit/protocols/data/__init__.py	True
pcapkit/protocols/data/application/httpv2.py	True
pcapkit/protocols/data/application/ospf.py	True
pcapkit/protocols/data/internet/hip.py	True
pcapkit/protocols/data/internet/hopopt.py	True
pcapkit/protocols/data/internet/ipv4.py	True
pcapkit/protocols/data/internet/ipv6.py	True
pcapkit/protocols/data/internet/ipv6_ext.py	True
pcapkit/protocols/data/internet/ipv6_opts.py	True
pcapkit/protocols/data/internet/mh.py	True
pcapkit/protocols/data/link/__init__.py	True
pcapkit/protocols/data/misc/null.py	True
pcapkit/protocols/data/misc/pcapng.py	True
pcapkit/protocols/data/transport/tcp.py	True

[github-actions]

Coverage: 88.74% (unit tier, Python 3.14, c420eaa58, Unit Tests run success)

Package	Statements	Missed	Branches	Partial	Cover
pcapkit (top level)	104	4	20	4	93.55%
pcapkit/const	18757	1035	2342	846	90.23%
pcapkit/corekit	1874	91	578	22	94.33%
pcapkit/dumpkit	136	0	40	0	100.00%
pcapkit/foundation	2422	143	842	34	92.62%
pcapkit/interface	112	7	40	5	92.11%
pcapkit/protocols	15653	187	3942	162	98.19%
pcapkit/toolkit	487	71	144	3	84.15%
pcapkit/utilities	429	4	122	4	98.55%
pcapkit/vendor	4409	2359	1006	158	42.84%

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

[JarryShaw]

Cross-review verdict on c420eaa58: GOOD TO GO (ran on Sonnet; author Opus)

• No code changed. All 14 files are AST-identical to origin/main once bare strings are stripped.
• IPv4.options exists only when hdr_len > 20. Probed with a 20-byte and a 24-byte header.
• HIP SolutionParameter.reserved is carried verbatim, and only PUZZLE uses _make_puzzle_lifetime. The :issue: link and RFC citations are kept.
• Info subclasses with no annotations get __init__(self, dict_=None, **kwargs). Probed.
• ipv6_ext protocol is None both when alias is absent and when the lookup misses.
• The #: fixes now register. ModuleAnalyzer.find_attr_docs() returns IPDFFOption.flags from both hopopt and ipv6_opts, plus TROption.originator and IPv4.options.
• "Reserved keyword" is correct everywhere. The typo fixes touch no identifiers.
• Tests: test_docstring_contract and 8 touched unit modules pass.
• Non-blocking: #: Return hop count. in TROption is still orphaned, as it is on main.