DESIGN.md: output depends on the installed CJK font extras #625

Context

DESIGN.md sections 10.1, 11, and 14. #600 (PR #613) makes the installed pylopdf-fonts-* packages the default faces of doc.fallback_fonts, so rendering output also depends on which of them are installed, as OcrEngine() already depends on pylopdf-ocr-models. Three sentences of DESIGN.md do not say so yet. The owner approved the wording proposed on #600 on 2026-11-04.

Goal

DESIGN.md says that output can depend on the installed data packages of section 14, and that the jp, ko, zh-cn, and zh-tw extras install the CJK faces.

Scope

In: the three sentences, with the approved wording. Out: any other change of DESIGN.md, and the implementation, which is PR #613.

Paths

DESIGN.md.

Acceptance

• Section 10.1 says that output depends on the data packages of section 14 that are installed, which the API that uses them documents.
• Section 11 says that the jp, ko, zh-cn, and zh-tw extras install the CJK faces that render the fonts that a document does not embed.
• Section 14 item 3 names the packages that those extras install.

Notes

The sentences are true only once PR #613 lands, so the pull request merges with or after it.