Add the German catalog: every menu string, every `tl!` literal, the plural
forms and the status and error messages (3,818 rows), written from the meaning
of the English labels in the vocabulary German-speaking users of vector
illustration software know (Zeichenfläche, Farbfelder, Kontur, Fläche, Pfad,
Ankerpunkt, Ebene, Verlauf, Deckkraft). Conventions are in the header of
`de.tsv`.
- Register `de` ("Deutsch") in `i18n::LANGUAGES` as a complete language; every
`de-*` locale (`de-DE`, `de-AT`, `de-CH` …) resolves to it.
- Tests: German joins the menu-label, menu-string, `tl!`-literal and message
coverage checks; `german_reads_as_german` pins the core vocabulary, the
plurals, a nested message, the joined "…format" style names and the theme
context ("Erscheinungsbild" vs the Appearance panel's "Aussehen"); ä ö Ä Ö ß
are checked in the bundled UI fonts. The "unsupported locale" cases use
Dutch now that German is supported.
- README, ROADMAP and docs/development.md list German.
Co-Authored-By: Claude Opus 5.5 <[email protected]>
