Publish ref docs to GitHub Pages with versioning and version picker

[kirre-bylund]

Part of lootlocker/index#1465.

What this does

Adds GitHub Pages deployment to the existing generate-docs.yml workflow so reference docs are publicly hosted at a stable URL, with full version history.

New: deploy-pages job

• Runs on push to main, release (published), and workflow_dispatch — not on PRs
• Deploys Doxygen HTML to the gh-pages branch:
  • latest/ — updated on every push to main / dispatch
  • v<tag>/ — additionally deployed on release events
• Maintains versions.json at the site root (semver-sorted descending, latest always first) so the version picker can discover all published versions
• Writes a root index.html that meta-redirects to latest/

New: version-picker.js

• Loaded via <script defer> in header.html
• On page load: fetches versions.json from the site root, replaces the static #ll-topnav-version span with a <select> dropdown
• Preserves the current page filename when switching versions (best-effort)
• Graceful no-op fallback when versions.json is absent (local builds — existing static badge is kept as-is)

CSS + Doxyfile

• lootlocker-theme.css: extends the existing #ll-topnav-version rule to also style #ll-version-picker; adds <select>-specific resets and hover/focus styles
• Doxyfile: adds version-picker.js to HTML_EXTRA_FILES

After merging

A repo admin needs to enable GitHub Pages in Settings → Pages:

• Source: branch gh-pages / / (root)
• No custom domain

Then trigger a workflow_dispatch on main to populate latest/ for the first time. The backend team will subsequently proxy ref.lootlocker.com/unreal/* → the Pages URL.

Files changed

File	Change
.github/workflows/generate-docs.yml	Add push trigger; add deploy-pages job
.doxygen/version-picker.js	New — version dropdown JS
.doxygen/Doxyfile	Add version-picker.js to HTML_EXTRA_FILES
.doxygen/header.html	Add <script defer> for version-picker.js
.doxygen/lootlocker-theme.css	Add <select> styles for version picker

[Copilot]

Pull request overview

This PR extends the existing Doxygen reference-doc generation pipeline to publish versioned docs to GitHub Pages (via gh-pages) and adds a client-side version picker in the generated HTML so users can switch between published doc versions.

Changes:

• Adds a deploy-pages job intended to publish generated docs to gh-pages and maintain a versions.json index plus a root redirect page.
• Introduces a version-picker.js script and wires it into the Doxygen HTML header to replace the static version badge with a <select> populated from versions.json.
• Updates Doxygen config/CSS to ship and style the version picker assets.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
.github/workflows/generate-docs.yml	Adds a Pages deployment job, generates versions.json, and publishes versioned directories to gh-pages.
.doxygen/version-picker.js	Implements the client-side version dropdown by fetching versions.json and navigating between versions.
.doxygen/Doxyfile	Includes version-picker.js as an extra HTML asset in the Doxygen output.
.doxygen/header.html	Loads version-picker.js via a deferred script tag.
.doxygen/lootlocker-theme.css	Styles the version picker to match the existing top navigation theme.