Superseded language-scope contracts

The v0.5.0 Typst-scope and keyboard-language routing contracts were replaced by the document-script model during v0.5.x development. They are not runtime contracts.

The current contract is documented in Document language tools: portable project metadata assigns at most one language to each ambiguous script, while scripts with one catalog language resolve automatically. Typst lang scopes and operating-system keyboard layouts do not reroute spellcheck or word completion.