Add typed text pages; serve CSS as compiled-on-demand /css/main.css

Sidecar-less page bundles whose directory ends in a MediaType extension
(.txt/.css/.xml/.json/.js) now render raw (no HTML layout, autoescape off),
are served with that extension's Content-Type, and cache as a flat file
(public/cache/<path>) so Apache serves them directly via a new .htaccess
rule. They're excluded from the content index.

CSS becomes one of these: novaconium/pages/css/main.css/ holds index.twig
({{ sass('main.sass') }}), main.sass, and _colors.sass. App\SassExtension's
sass() Twig function resolves the entry file through the overlay and shells
out to Dart Sass on a cache miss; Lib\SassCompiler wraps the CLI. This
drops the committed App/css/main.css build artifact and the public/css
bind mount. Override styling by copying the whole bundle to App/pages/.

Also ship robots.txt and humans.txt as framework bundles, and drop the
php -S dev router (public/router.php) - Docker/Apache only now.

New: novaconium/src/MediaType.php, SassExtension.php, lib/SassCompiler.php.
Moved: novaconium/sass/ -> novaconium/pages/css/main.css/ (+ App/sass merged).
Docs: AGENTS.md, new /admin/docs/text-pages, and styling/caching/docker/
design-notes/getting-started/project-layout/config docs updated.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018Q9cAXC9xcXYnmP7qjsnw7

docker-compose.yml

@@ -5,7 +5,6 @@ services:
       - "8080:80"
     volumes:
       - ${PROJECT_PATH:-/data}:/var/www/html/App
-      - ${PROJECT_PATH:-/data}/css:/var/www/html/public/css
       - ${VOL_PATH:-/data}/novaconium/cache:/var/www/html/public/cache
       - ${VOL_PATH:-/data}/novaconium/uploads:/var/www/html/public/uploads
       - ${VOL_PATH:-/data}/novaconium/data:/var/www/html/data