Dokumentschema v17: Projektraster, verlinktes Bild, klebender Kopfbereich

Alles aus dem Nachbau von kant-it.de, den Umut durchgesehen hat.

Eine Beitragsliste kann Datum, Autor, Auszug und Kategorie ausblenden und
sieht damit aus wie ein Projektraster statt wie ein Blogarchiv. Beinahe
lautlos danebengegangen: |default(true) macht in Twig aus einem
gespeicherten false ein true - die Einstellung haette sich speichern
lassen und nichts getan. Der Test prueft beide Richtungen.

Ein Bild darf verlinken, damit ein Logo auf die Startseite zeigt; die
Adresse geht durch dieselbe Pruefung wie jeder andere Link. Und der
Kopfbereich kann beim Scrollen oben bleiben - als Einstellung der
Website, weil nur das umschliessende Element kleben kann.

Der groesste Fund steckt im Editor: die Liste bekannter Schemafassungen
endete bei 12, waehrend Bausteine v13 bis v15 verlangen. In einem
aktuellen Dokument liess sich damit kein Baustein mehr einfuegen, und
Symbol, Fortschritt, Slider und externer Inhalt in gar keinem. Jetzt eine
Zahl an einer Stelle, mit einem Test ueber jeden Typ und jede Fassung.

Geprueft: 389 PHP-Tests unter 8.2 und 8.4, 18 JS-Tests, Editortest,
Browserpruefung.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

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