[Exeloo]

What does this PR do?

No linked issue: this is a full audit of the engine user docs, requested directly. Every page was checked against the current packages and modules, then fixed or rewritten for game developers.

• Getting started: what the engine is, a table of its 13 packages, and "Create a project" with nf new. New pages: a quickstart 2D game, and core concepts (factory, app.use/init/run, libraries, context, loop hooks, ECS, client/server split, writing a library).
• New module pages: ecs, graphics-2d, input, audio, assets, scene, env.
• Fixed:
  • network: setup, env var tables, wrong types and claims, duplicate API examples cut.
  • graphics-3d: complete examples, viewport and camera notes.
  • editor protocol: every feature and command.
  • README: package list and docs link.
• Moved out of the site: the 3D library benchmark and the editor proposal go to docs/design/. The docs repo PR adds redirects for them.
• registry/* is relabelled "ECS internals". No other slug changed.

How do you test this PR?

• Before: getting started had 160 words and no runnable path. README listed 7 package names that no longer exist. Pages named network-client/network-server packages, and the ECS page claimed class renaming by bundlers was harmless.
• After: the pages match the code. The quickstart and module snippets pass tsc --noEmit against the built packages. The game itself was not run in a browser.
• docs-sync check, then mint validate, mint broken-links and mint a11y on a scratch copy of the site with all four source branches (engine, cli, loader, editor) and the docs redirects synced in: all pass, 83 pages.
• pnpm exec prettier --check and the pre-push hook (lint, tests): pass.

Merge danger

Door: two-way, docs only: a revert is enough.
Blast radius: the public docs.nanoforge.eu, at this repo's next release (docs-sync), not at merge.

Follow-up issues

To be filed: the client-only nf new sample fails without a .env (cli); LibraryRelationships TSDoc contradicts runBefore/runAfter; stale README and TSDoc examples (asset, ecs, sound, music, core, editor-lib, network ICE_SERVERS).

Quality gate

Lane	Result
Docs	the change is docs
Correctness	independent reviewer: findings fixed in the last commit
Accessibility (content)	pass (alt text, headings, link text; mint a11y)
Security (content)	pass, no secrets or internal URLs
Style	style-reviewer: pass
Performance	N/A (docs)