Redesign landing page to match TypeDoc 0.28 look and feel

[willeastcott]

What changed

The landing page hand-mimicked an old (~v0.22-era) TypeDoc theme and had drifted visually from the TypeDoc 0.28 output of the actual product references (different palette, toolbar, theme semantics). This PR rewrites it to be faithful to TypeDoc 0.28 and fixes several accumulated bugs.

Landing page (index.html, now a build-time template + assets/landing.css)

• Reuses TypeDoc's actual generated stylesheet instead of duplicating theme CSS: build.mjs copies docs/engine/assets/style.css + icons.svg into docs/assets/, and the landing page layers a small landing.css on top (TypeDoc wraps its rules in @layer typedoc, so unlayered overrides need no specificity hacks). When product repos bump TypeDoc, the landing page restyles itself automatically — the drift that motivated this rewrite can't recur.
• Mirrors TypeDoc 0.28 markup: tsd-page-toolbar, container-main grid, sidebar with Settings accordion, tsd-generator footer.
• Cards grouped into PlayCanvas Development (Engine, Editor, React, Web Components) and Foundational Libraries (PCUI, PCUI Graph, Observer, Splat Transform), with version badges injected at build time from each cloned repo's package.json. The sidebar nav mirrors the card grid so they can't drift apart.
• Tri-state os/light/dark theme matching TypeDoc 0.28's tsd-theme localStorage semantics.

Bug fixes

• Footer "generated on" date was client-side new Date() — it showed the visitor's date, not the build date. Now injected at build time.
• The old theme toggle force-wrote dark to localStorage on page load, silently overriding the user's OS preference across all doc pages. The new page only writes on an explicit user change.
• The mobile menu button toggled a CSS class that had no styles (dead button). It now reuses TypeDoc's own has-menu drawer.
• Removed the card-filter "search" (it only filtered the 8 cards; a cross-product search over the TypeDoc indexes is a possible follow-up).

Build pipeline (build.mjs)

• generateLandingPage() — replaces {{BUILD_DATE}} / {{VERSION:*}} tokens; missing versions degrade to no badge with a warning.
• copySharedAssets() — shares TypeDoc's stylesheet/icons with the landing page.
• postProcessProductDocs() — makes the route back to the landing page obvious on every generated product page: the toolbar title becomes a breadcrumb (Home / Engine API Reference - v2.19.1) and the sidebar "Home" link is renamed to "← All API References". Idempotent, runs over all ~2,250 generated pages.
• --landing-only flag (npm run build:landing) regenerates just the landing page + post-processing against an existing docs/, skipping the slow 8-repo clone/build loop for local iteration.

Reviewer notes

• Verified locally (npm run build:landing + npm run serve): visual parity with /engine/ in light/dark/OS modes, theme persistence in both directions between landing and product pages, all product links resolve, mobile drawer opens/closes, console clean, no template tokens leak into output.
• The full pipeline path (fresh clone of all 8 repos) is unchanged apart from the new steps at the end; the first Pages deploy after merge is worth watching to confirm end-to-end.
• The breadcrumb hides below 770px to avoid crowding the mobile toolbar; mobile users still get the renamed sidebar link.

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR updates the root landing page and build pipeline so the landing experience matches TypeDoc 0.28 styling/markup and stays visually in-sync by reusing TypeDoc-generated theme assets, while also post-processing generated product docs to improve navigation back to the landing page.

Changes:

• Replace the legacy hand-styled landing page with a TypeDoc 0.28-aligned template that layers minimal custom CSS over the shared TypeDoc stylesheet.
• Extend build.mjs to generate the landing page at build time (injecting build date + per-repo versions), copy shared TypeDoc assets, and post-process generated docs to add a “Home” breadcrumb and rename the sidebar Home link.
• Add npm run build:landing to regenerate only the landing page + post-processing against an existing docs/ for faster iteration.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 7 comments.

File	Description
package.json	Adds a build:landing script to run the build in landing-only mode.
index.html	Replaces the landing page markup/scripts to mirror TypeDoc 0.28 and adds build-time tokens for versions/date.
build.mjs	Adds landing generation, shared asset copying, product-doc post-processing, and the --landing-only path.
assets/landing.css	Adds minimal landing-specific styling intended to override TypeDoc’s layered CSS.

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[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated no new comments.