docs: add Google Analytics

[shenxianpeng]

These docs are served from the cpp-linter.github.io origin, but unlike the organization site they have no Google Analytics. So there is no record of what readers look at once they leave the organization's home page. This PR adds the same property the organization site uses (G-JKH4SXC7HC). It also adds the maintainer flag from cpp-linter/cpp-linter.github.io#83, so the maintainers' own reading can be filtered out.

This PR only changes the site. The Google Analytics side (the Internal Traffic filter, key events) is handled separately.

Before / After (改动前 / 改动后)

	Before (live site, origin/main)	After (this branch)
Google Analytics	No gtag on any page	G-JKH4SXC7HC on every page
Maintainer visits	—	traffic_type=internal while the cpp-linter-internal flag is set (?internal=1 / ?internal=0 on any page of the origin)
404 page <title>	Cpp-Linter (same as the home page)	Page not found - Cpp-Linter

The overrides live in docs/overrides/, next to docs/docs/, so they are not published as pages.

Evidence: built <head> of index.html

<script>
  try {
    var param = new URLSearchParams(location.search).get("internal");
    if (param === "1") localStorage.setItem("cpp-linter-internal", "1");
    if (param === "0") localStorage.removeItem("cpp-linter-internal");
    if (localStorage.getItem("cpp-linter-internal") === "1") {
      window.dataLayer = window.dataLayer || [];
      (function () { dataLayer.push(arguments); })("set", { traffic_type: "internal" });
    }
  } catch (e) {
    // localStorage is unavailable when storage is blocked; the visit is then not tagged.
  }
</script>
<script id="__analytics">function __md_analytics(){ /* … the theme's snippet, unchanged … */ var t=document.createElement("script");t.async=!0,t.src="https://www.googletagmanager.com/gtag/js?id=G-JKH4SXC7HC",document.getElementById("__analytics").insertAdjacentElement("afterEnd",t)}</script>

I did not run the full docs build locally, because it compiles the Rust CLI generator. The theme changes were built with the same mkdocs 1.6.1 / mkdocs-material 9.7.7 pins from docs/pyproject.toml, with a temporary config that inherits docs/mkdocs.yml and leaves out the gen-files plugins and the other nav pages. The Build docs job in this PR runs the full build.

Notes

• The flag snippet runs in the theme's analytics block, before the theme's own snippet. That way gtag('set', {traffic_type: 'internal'}) is queued ahead of the first page_view. The same snippet was tested end to end with the real gtag.js and a fake measurement ID in feat: tag maintainer visits, track code copies and add social cards cpp-linter.github.io#83: tt=internal is sent after ?internal=1 and stops after ?internal=0.
• None of these changes alters a page's layout, so there are no screenshots.
• cspell.config.yml gains htmltitle (a Jinja block name in docs/overrides/404.html).

Summary by CodeRabbit

• Documentation
  • Added a custom “404 - Not found” page to the documentation site.
  • Configured Google Analytics for the documentation site, including support for distinguishing internally tagged visits.
  • Updated the documentation theme configuration to load custom overrides.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

• Configuration used: Repository UI (base), Organization UI (inherited)
• Review profile: CHILL
• Plan: Advanced
• Run ID: c87be8f2-3d98-451e-b074-0b04a489d255

📥 Commits

Reviewing files that changed from the base of the PR and between d8c28eb and 973201d.

📒 Files selected for processing: 4

• cspell.config.yml
• docs/mkdocs.yml
• docs/overrides/404.html
• docs/overrides/main.html

Included review availability: This review used your included allowance. Your plan provides up to 1 included review per hour; 0 remain after this review.

📝 Walkthrough

The documentation configuration now loads theme overrides and Google Analytics. The main override handles internal-traffic classification. A custom 404 template renders a page-specific title and heading, and the spell-checker word list includes htmltitle.

Changes: Documentation analytics and templates

Layer / File(s)	Summary
Configure analytics and internal-traffic handling docs/mkdocs.yml, docs/overrides/main.html	MkDocs configures the override directory and Google Analytics property. The main template updates the internal-traffic flag from the internal query parameter and queues traffic_type=internal when the flag is set.
Render the 404 page docs/overrides/404.html, cspell.config.yml	The 404 template extends main.html, sets a title using the site name, and renders a “404 - Not found” heading. The spell-checker word list adds htmltitle.

Priority: ⬇️ Low

Estimated code review effort: 2 (Simple) | ~10 minutes

Merge Risk: ⚪ Minimal · up to 97320

This change adds Google Analytics internal-traffic tagging and a custom 404 page. The inspected templates match the pinned theme behavior, and no actionable merge-blocking risk remains.

Pre-merge checks: 5

Check name	Status	Explanation
Docstring Coverage		No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0…
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title clearly and concisely identifies the primary change: adding Google Analytics to the documentation site.

Full details: Docstring Coverage

Explanation

No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0 files. (4 skipped: 4 unsupported.)

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[2bndy5]

FYI, I have an DNS sink hole filtering out most HTTP requests for ads and analytics across my entire network. It works great for blocking full-page ads in mobile apps 😉. So, this analytics stuff is all you; I can't even log in to Google Analytics site without explicitly whitelisting the domain...

[shenxianpeng]

Haha, makes sense 😄 No worries, I’ll take care of the analytics side. I have added you to the GA property just in case. if you can not visit it pls let me know.