i18n: Japanese for the panels, dialogs and tooltips

ui.rs gets a Japanese table with the same 396 rows as the Simplified and
Traditional Chinese ones, so Japanese now translates the interface below
the menu bar too (it covered the menus only). The shape test keeps the
three tables listing the same source strings; a new test checks that
Japanese reads its own rows and fills values in order. The existing
"no rows yet" check uses Ukrainian instead.

ROADMAP.md and docs/preferences.md say which catalogs have panel rows.

Co-Authored-By: Claude Sonnet 5.5 <[email protected]>

docs/preferences.md

@@ -29,7 +29,7 @@ Commands (CLI, MCP, control channel):
 
 ### Settings that change behaviour
 
-- `general.language`: interface language (`system` / `en` / `ja` / `zh-hans` / `zh-hant` / `uk`), Settings ▸ General ▸ Language; menu labels change immediately. `system` (Match System, the default) follows the operating system's interface language where EffectCraft has a translation and is English otherwise: a Simplified Chinese locale (`zh`, `zh-CN`, `zh_CN.UTF-8`, `zh-Hans-CN`, `zh-SG`) selects `zh-hans`, a Traditional one (`zh-TW`, `zh-HK`, `zh-Hant`, `zh_MO`) selects `zh-hant`, a Ukrainian one (`uk`, `uk-UA`, `uk_UA.UTF-8`) selects `uk`; the browser build stays in English with it. Choose **Українська** for Ukrainian menus; Ukrainian dialog and panel contents stay in English for now, and Ukrainian uses the bundled UI fonts. Native Japanese, Simplified and Traditional Chinese UI uses installed system fonts; the web host must supply a Japanese font. The same setting picks the CJK fallback for the interface *and* the Han preference of the text engine, so the composition's own text is drawn with the same language's glyph forms (the text engine's preference is process-global); swapping the language reinstalls the fonts, so it applies without a restart. Two catalogs back the text: the menus are keyed by `(command, English label)` (`crates/ui-egui/src/i18n.rs`), and the rest of the interface - panels, dialogs, buttons, tooltips - is keyed by its English source string (`crates/ui-egui/src/i18n/ui.rs`), where a panel writes `tr("Rename")`, or `tr_args("Proxy Use: {}", &[&quality])` when the row carries a value. A row that is missing falls back to English, so a new string shows up untranslated rather than empty; the tests in that module fail on an unused row and on a hard-coded string in a converted panel.
+- `general.language`: interface language (`system` / `en` / `ja` / `zh-hans` / `zh-hant` / `uk`), Settings ▸ General ▸ Language; menu labels change immediately. `system` (Match System, the default) follows the operating system's interface language where EffectCraft has a translation and is English otherwise: a Simplified Chinese locale (`zh`, `zh-CN`, `zh_CN.UTF-8`, `zh-Hans-CN`, `zh-SG`) selects `zh-hans`, a Traditional one (`zh-TW`, `zh-HK`, `zh-Hant`, `zh_MO`) selects `zh-hant`, a Ukrainian one (`uk`, `uk-UA`, `uk_UA.UTF-8`) selects `uk`; the browser build stays in English with it. Choose **Українська** for Ukrainian menus; Ukrainian dialog and panel contents stay in English for now, and Ukrainian uses the bundled UI fonts. Native Japanese, Simplified and Traditional Chinese UI uses installed system fonts; the web host must supply a Japanese font. The same setting picks the CJK fallback for the interface *and* the Han preference of the text engine, so the composition's own text is drawn with the same language's glyph forms (the text engine's preference is process-global); swapping the language reinstalls the fonts, so it applies without a restart. Two catalogs back the text: the menus are keyed by `(command, English label)` (`crates/ui-egui/src/i18n.rs`), and the rest of the interface - panels, dialogs, buttons, tooltips - is keyed by its English source string (`crates/ui-egui/src/i18n/ui.rs`, with rows for Japanese, Simplified Chinese and Traditional Chinese), where a panel writes `tr("Rename")`, or `tr_args("Proxy Use: {}", &[&quality])` when the row carries a value. A row that is missing falls back to English, so a new string shows up untranslated rather than empty; the tests in that module fail on an unused row and on a hard-coded string in a converted panel.
 - `general.undoLevels`: Levels of Undo
 - `general.pathPointSize`: Path Point and Handle Size
 - `general.recentItems`: Recent Projects Shown