docs(protocols): second whole-repo pass over internet (#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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Summary

#1103 second whole-repo pass, internet slice.

1.5.0 directives:

• versionchanged on the 19 HIP and 8 IPv4 data models that gained a
  required field, each citing the issue the field came from.
• hopopt, ipv6_opts and ipv4 pages gain the QuickStartRequestOption and
  QuickStartReportOption data models, so their directives render.

1.1.0-1.4.1 backfill:

• versionremoved:: 1.1.0 for the MH BindRefreshAdviceOption and
  BindingAuthorizationDataOption names, data and schema.
• versionchanged:: 1.3.0 on Internet.register (protocol argument).
• versionchanged:: 1.3.4 on IPv6_Route: length is in octets (ipv6 packet with option decodes error #218).

Accuracy:

• RFC 6275 citations for Pad1, PadN and MH padding name 6.2.2, 6.2.3
  and 6.1.1, not 6.2.5 (Alternate Care-of Address).
• generic_ext_codes no longer cites the shim6 placeholder path.

Rendering: PadOption length references point at the Option fields
that define them; _SMFDPDOption is documented; IPv6_Ext.next no
longer points at a type-checking-only class.

AST identical on all 12 .py files; tests/project and 95 related pass.

Refs #1103

[JarryShaw]

Verdict: GOOD TO GO at d744d7275. A Sonnet cross-review (author: Opus) found no blocking findings. Scope stays inside the slice, the AST guard is identical against main, and every directive was checked against the release tags. The merged build of all nine second-pass heads has 18 warnings, the same as main. tests/project: 950 passed, 1 skipped, 3670 subtests passed.