Merge #311: i18n: translate the whole interface into German

Conflict: ROADMAP.md: next's right-to-left and interface-language lines, with #311's sentence that German and Japanese cover every key.

ROADMAP.md

@@ -140,7 +140,7 @@ DesignCraft aims at full Adobe InDesign parity — and to be better: faster, ope
 - Transparency flattener (`file.exportPdf {flatten: high|medium|low|ppi}`, Edit ▸ Transparency Flattener Presets): each object involving transparency becomes an opaque image of its area over what's beneath it, so everything else stays vector (spreads with transparent parent items are rasterised whole).
 - Video and sound (place .mp4/.mov/.webm/.mp3/.wav…, `media.options/get`, Media panel): media frames show a poster or placeholder on screen, in print and in PDF, and export as HTML5 `<video>`/`<audio>` in EPUB. Interactive PDF export (`file.exportPdf {media: true}`, File ▸ Export PDF (Interactive)) embeds each file and plays it in a Screen annotation through a rendition action (controls, loop, play on page load). No in-app playback.
 - Right-to-left text (World-Ready basics): right-to-left runs are shaped right to left, lines are reordered by the Unicode Bidirectional Algorithm (matched against the reference implementation), Paragraph Direction (`type.para {direction}`, Paragraph panel, IDML ParagraphDirection, EPUB `dir`). Digits (`digits`: Default, Arabic, Hindi, Farsi, Native by language; Character panel for right-to-left text; IDML DigitsType) draw 0–9 in another script. Kashidas (`kashidas` paragraph attribute, on by default; IDML Kashidas): justified Arabic lines stretch at one join per word (after seen/sad when possible, never inside lam–alef) with a drawn tatweel before word spaces widen. Carets follow the drawing: the caret before a right-to-left glyph sits at its right edge, arrow keys move as drawn (by words in the line's direction), clicks find the nearest drawn caret position and selections highlight the selected glyphs. Binding: Right to Left (Document Setup, `layout.documentSetup {binding}`, IDML PageBinding) makes page 1 a left page and lays spreads out right to left.
-- Interface language (Edit ▸ Interface Language, `app.language`): German, French, Spanish, Italian, Japanese, Simplified Chinese and Arabic menu titles, common menu items and panel names (our own translations). Common dialog, panel and tooltip labels are also localized, with English fallback for untranslated strings. Arabic translations cover every key in the shared interface translation table, including menu commands and utility labels. The Type menu's Story Direction, Horizontal/Vertical, Tate-Chu-Yoko, Ruby… and Kenten are translated too. Arabic labels use Unicode bidi run ordering and contextual shaping; welcome and new-document form layouts follow RTL direction independently of document binding. CJK and Arabic glyphs come from [craft-fonts](https://github.com/storytold/craft-fonts) when built with `CRAFT_FONTS_DIR` (all releases): BIZ UDPGothic and Noto Sans CJK SC for the UI (Chinese forms first in the Chinese interface), Noto Sans Arabic, and Mincho for Japanese documents (the web build embeds BIZ UDPGothic only); otherwise from system fonts. Ukrainian covers every catalog key, including publishing dialogs and built-in names, with persisted selection, grammatical count captions, English fallback and bundled Cyrillic UI glyph coverage.
+- Interface language (Edit ▸ Interface Language, `app.language`): German, French, Spanish, Italian, Japanese, Simplified Chinese and Arabic menu titles, common menu items and panel names (our own translations). Common dialog, panel and tooltip labels are also localized, with English fallback for untranslated strings. German and Japanese cover every key of every catalog. Arabic translations cover every key in the shared interface translation table, including menu commands and utility labels. The Type menu's Story Direction, Horizontal/Vertical, Tate-Chu-Yoko, Ruby… and Kenten are translated too. Arabic labels use Unicode bidi run ordering and contextual shaping; welcome and new-document form layouts follow RTL direction independently of document binding. CJK and Arabic glyphs come from [craft-fonts](https://github.com/storytold/craft-fonts) when built with `CRAFT_FONTS_DIR` (all releases): BIZ UDPGothic and Noto Sans CJK SC for the UI (Chinese forms first in the Chinese interface), Noto Sans Arabic, and Mincho for Japanese documents (the web build embeds BIZ UDPGothic only); otherwise from system fonts. Ukrainian covers every catalog key, including publishing dialogs and built-in names, with persisted selection, grammatical count captions, English fallback and bundled Cyrillic UI glyph coverage.
 - Page transitions (`page.transition/transitions`, Page Transitions panel): twelve transition types with speed and direction per spread, written into exported PDFs as `/Trans` entries through an incremental update.
 - PDF/X-4 export (`file.exportPdf {standard: "x4"}`): an output intent with our own Generic CMYK ICC profile (lut16 tables generated from the parametric press model), GTS_PDFXVersion in Info and XMP, `pdf:Trapped` in XMP as in Info, RGB images without a profile tagged sRGB, no image interpolation (none in PDF/A either), and built-in PDF/X-4 checks reported as warnings. qpdf finds no errors in the result.
 - EPS place: placed at its (high-resolution) bounding box and shown, printed and exported through its TIFF preview, or a placeholder when it has none. PostScript itself isn't interpreted.

crates/ui-egui/src/i18n.rs

@@ -4,6 +4,7 @@
 use std::{collections::HashMap, sync::OnceLock};
 
 mod ar;
+mod de;
 mod it;
 mod ja;
 mod pt_br;
@@ -2848,6 +2849,7 @@ fn column(lang: &str) -> Option<usize> {
 
 /// `s` in `lang` (English, or the string itself, when there's no translation).
 pub fn tr<'a>(lang: &str, s: &'a str) -> &'a str {
+    static GERMAN: OnceLock<HashMap<&'static str, &'static str>> = OnceLock::new();
     static JAPANESE: OnceLock<HashMap<&'static str, &'static str>> = OnceLock::new();
     static TRANSLATIONS: OnceLock<HashMap<&'static str, [&'static str; 5]>> = OnceLock::new();
     static ARABIC: OnceLock<HashMap<&'static str, &'static str>> = OnceLock::new();
@@ -2857,8 +2859,13 @@ pub fn tr<'a>(lang: &str, s: &'a str) -> &'a str {
     if lang == "ar" {
         return ARABIC.get_or_init(|| ar::TABLE.iter().copied().collect()).get(s).copied().unwrap_or(s);
     }
-    // The Japanese table covers the whole interface; the shared table's Japanese column is the fallback
-    // for keys added there after it.
+    // The German and Japanese tables cover the whole interface; the shared table's German and Japanese
+    // columns are the fallback for keys added there after them.
+    if lang == "de"
+        && let Some(text) = GERMAN.get_or_init(|| de::TABLE.iter().copied().collect()).get(s).copied()
+    {
+        return text;
+    }
     if lang == "ja"
         && let Some(text) = JAPANESE.get_or_init(|| ja::TABLE.iter().copied().collect()).get(s).copied()
     {
@@ -2920,13 +2927,16 @@ mod tests {
     fn cached_lookup_preserves_every_translation_across_language_switches() {
         for (key, translations) in TABLE {
             for (lang, expected) in ["de", "fr", "es", "ja", "zh"].into_iter().zip(translations) {
-                // `ja::TABLE` translates the whole interface and wins over the shared Japanese column.
-                if lang != "ja" {
+                // `de::TABLE` and `ja::TABLE` translate the whole interface and win over the shared columns.
+                if lang != "de" && lang != "ja" {
                     assert_eq!(tr(lang, key), *expected, "{lang}: {key}");
                 }
             }
             assert_eq!(tr("", key), *key);
         }
+        for (key, expected) in de::TABLE {
+            assert_eq!(tr("de", key), *expected, "de: {key}");
+        }
         for (key, expected) in ar::TABLE {
             assert_eq!(tr("ar", key), *expected, "ar: {key}");
         }