feat(ui): add ja-JP locale and split i18n into per-language modules (#372)

The single en/zh tuple table becomes one module per language behind a
`SUPPORTED_LANGUAGES` table, and Japanese joins English and Simplified Chinese.

- `gui_language` accepts `ja-JP`; anything unrecognized still falls back to `en`.
- The language picker and `refresh_locale_state` both read `SUPPORTED_LANGUAGES`
  instead of keeping their own copy of the code list.
- Language names in the picker stay endonyms (English / 简体中文 / 日本語) in
  every locale, as English and Chinese already were.
- The zh and ja key tables are exhaustive, so a new `L10nKey` fails the build
  until it is translated rather than silently rendering English.

Co-authored-by: Chihiro WATANABE <chihiro.watanabe@live.jp>

crates/tty7-core/src/core/config.rs

@@ -4,6 +4,8 @@ use std::sync::{Arc, OnceLock};
 
 use serde::{Deserialize, Serialize};
 
+pub const SUPPORTED_GUI_LANGUAGES: &[&str] = &["en", "zh-CN", "ja-JP"];
+
 #[derive(Default, Clone, Eq, PartialEq, Hash)]
 pub struct FontFeatures(pub Arc<Vec<(String, u32)>>);
 
@@ -519,9 +521,8 @@ impl Config {
             .take()
             .map(|proxy| proxy.trim().to_string())
             .filter(|proxy| !proxy.is_empty());
-        match self.gui_language.as_str() {
-            "en" | "zh-CN" => {}
-            _ => self.gui_language = default_gui_language(),
+        if !SUPPORTED_GUI_LANGUAGES.contains(&self.gui_language.as_str()) {
+            self.gui_language = default_gui_language();
         }
     }
 
@@ -1138,6 +1139,9 @@ mod tests {
         let cfg: Config = serde_json::from_str(r#"{"gui_language": "zh-CN"}"#).unwrap();
         assert_eq!(cfg.gui_language, "zh-CN");
 
+        let cfg: Config = serde_json::from_str(r#"{"gui_language": "ja-JP"}"#).unwrap();
+        assert_eq!(cfg.gui_language, "ja-JP");
+
         let mut cfg: Config = serde_json::from_str(r#"{"gui_language": "ko"}"#).unwrap();
         cfg.sanitize();
         assert_eq!(cfg.gui_language, "en");

docs/features.md

@@ -143,13 +143,14 @@ whatever you ran in the pane, and you can revoke it under Privacy & Security.
 
 ## Localization
 
-The GUI ships English and Simplified Chinese strings. Pick one in Settings →
-Appearance → Language, or in `config.json`:
+The GUI ships English, Simplified Chinese and Japanese strings. Pick one in
+Settings → Appearance → Language, or in `config.json`:
 
 ```json
 { "gui_language": "zh-CN" }
 ```
 
-`en` and `zh-CN` are the only accepted values; anything else falls back to `en`.
+`en`, `zh-CN` and `ja-JP` are the only accepted values; anything else falls back
+to `en`.
 The choice is explicit — the system language is never inferred. CLI output stays
 English so agent and script integrations keep a stable, predictable surface.

docs/features.zh-CN.md

@@ -137,12 +137,12 @@ Apple Events、系统管理），这样程序才能正常弹出一次性授权
 
 ## 本地化
 
-GUI 目前提供英文和简体中文两套文案。在「设置 → 外观 → 语言」中选择，或直接改
+GUI 目前提供英文、简体中文和日文三套文案。在「设置 → 外观 → 语言」中选择，或直接改
 `config.json`：
 
 ```json
 { "gui_language": "zh-CN" }
 ```
 
-只接受 `en` 和 `zh-CN` 两个值，其它值一律回落到 `en`。语言必须显式指定，不会
+只接受 `en`、`zh-CN` 和 `ja-JP` 三个值，其它值一律回落到 `en`。语言必须显式指定，不会
 去猜系统语言。CLI 输出保持英文，保证 agent、脚本和开发者工作流的输出稳定可预测。

src/ui/app.rs

@@ -3702,17 +3702,19 @@ impl Tty7App {
         window: &mut Window,
         cx: &mut Context<Self>,
     ) -> Entity<SelectState<SearchableVec<String>>> {
-        const CODES: &[&str] = &["en", "zh-CN"];
         let labels = || {
-            vec![
-                t(L10nKey::SettingsLanguageEnglish).to_string(),
-                t(L10nKey::SettingsLanguageChinese).to_string(),
-            ]
+            crate::ui::i18n::SUPPORTED_LANGUAGES
+                .iter()
+                .map(|lang| t(lang.label_key).to_string())
+                .collect::<Vec<_>>()
         };
         let cfg = cx.global::<Config>();
         let current = Self::normalize_gui_language(&cfg.gui_language);
         let rows = labels();
-        let selected = CODES.iter().position(|c| *c == current).unwrap_or(0);
+        let selected = crate::ui::i18n::SUPPORTED_LANGUAGES
+            .iter()
+            .position(|lang| lang.code == current)
+            .unwrap_or(0);
         let language_select = cx.new(|cx| {
             SelectState::new(
                 SearchableVec::new(rows),
@@ -3728,7 +3730,9 @@ impl Tty7App {
                 if let SelectEvent::Confirm(Some(label)) = ev {
                     let rows = labels();
                     if let Some(idx) = rows.iter().position(|r| r == label) {
-                        this.set_gui_language(CODES[idx], window, cx);
+                        if let Some(lang) = crate::ui::i18n::SUPPORTED_LANGUAGES.get(idx) {
+                            this.set_gui_language(lang.code, window, cx);
+                        }
                     }
                 }
             },
@@ -3737,10 +3741,9 @@ impl Tty7App {
     }
 
     fn normalize_gui_language(code: &str) -> &'static str {
-        match code {
-            "zh-CN" => "zh-CN",
-            _ => "en",
-        }
+        crate::ui::i18n::find_language(code)
+            .map(|lang| lang.code)
+            .unwrap_or_else(crate::ui::i18n::default_language_code)
     }
 
     pub(crate) fn set_gui_language(
@@ -3762,7 +3765,6 @@ impl Tty7App {
     }
 
     pub(crate) fn refresh_locale_state(&mut self, window: &mut Window, cx: &mut Context<Self>) {
-        const CODES: &[&str] = &["en", "zh-CN"];
         self.sidebar_search.update(cx, |state, cx| {
             state.set_placeholder(t(L10nKey::SearchTabs), window, cx)
         });
@@ -3770,14 +3772,17 @@ impl Tty7App {
             state.set_placeholder(t(L10nKey::SearchFiles), window, cx)
         });
         if let Some(s) = self.active_settings() {
-            let rows = vec![
-                t(L10nKey::SettingsLanguageEnglish).to_string(),
-                t(L10nKey::SettingsLanguageChinese).to_string(),
-            ];
+            let rows = crate::ui::i18n::SUPPORTED_LANGUAGES
+                .iter()
+                .map(|lang| t(lang.label_key).to_string())
+                .collect::<Vec<_>>();
             s.language_select.update(cx, |state, cx| {
                 state.set_items(SearchableVec::new(rows), window, cx);
                 let code = Self::normalize_gui_language(&cx.global::<Config>().gui_language);
-                let selected = CODES.iter().position(|c| *c == code).unwrap_or(0);
+                let selected = crate::ui::i18n::SUPPORTED_LANGUAGES
+                    .iter()
+                    .position(|lang| lang.code == code)
+                    .unwrap_or(0);
                 state.set_selected_index(Some(IndexPath::default().row(selected)), window, cx);
             });
             s.search.update(cx, |state, cx| {