i18n: add Thai (th) interface language

A clean-room Thai catalog covering every key the bundled catalogs translate, its LANGUAGES row (one plural form) and Thai month and weekday names in DATE_LANGUAGES.

crates/engine/src/dates.rs

@@ -56,7 +56,7 @@ const AR_DAYS: [&str; 7] = ["الأحد", "الاثنين", "الثلاثاء",
 
 /// The languages month and weekday names can be written in (Preferences ▸ Date format ▸ Language):
 /// the interface languages, in the same order and with the same names.
-pub static DATE_LANGUAGES: [DateLanguage; 23] = [
+pub static DATE_LANGUAGES: [DateLanguage; 24] = [
     DateLanguage {
         code: "en",
         name: "English",
@@ -398,6 +398,15 @@ pub static DATE_LANGUAGES: [DateLanguage; 23] = [
         days: ["Chủ Nhật", "Thứ Hai", "Thứ Ba", "Thứ Tư", "Thứ Năm", "Thứ Sáu", "Thứ Bảy"],
         days_short: ["CN", "T2", "T3", "T4", "T5", "T6", "T7"],
     },
+    DateLanguage {
+        code: "th",
+        name: "ไทย",
+        months: ["มกราคม", "กุมภาพันธ์", "มีนาคม", "เมษายน", "พฤษภาคม", "มิถุนายน", "กรกฎาคม", "สิงหาคม", "กันยายน", "ตุลาคม", "พฤศจิกายน", "ธันวาคม"],
+        months_with_day: None,
+        months_short: ["ม.ค.", "ก.พ.", "มี.ค.", "เม.ย.", "พ.ค.", "มิ.ย.", "ก.ค.", "ส.ค.", "ก.ย.", "ต.ค.", "พ.ย.", "ธ.ค."],
+        days: ["วันอาทิตย์", "วันจันทร์", "วันอังคาร", "วันพุธ", "วันพฤหัสบดี", "วันศุกร์", "วันเสาร์"],
+        days_short: ["อา.", "จ.", "อ.", "พ.", "พฤ.", "ศ.", "ส."],
+    },
 ];
 
 /// The date language for `code` (any case), or `None` when there's none.

crates/ui-egui/src/i18n/mod.rs

@@ -147,7 +147,7 @@ fn plural_sl(n: u64) -> usize {
 }
 
 /// The registry. English first: it is the fallback and the source language.
-pub static LANGUAGES: [LangInfo; 23] = [
+pub static LANGUAGES: [LangInfo; 24] = [
     LangInfo { code: "en", name: "English", source: "", plural: plural_one_other, rtl: false, catalog: OnceLock::new() },
     LangInfo { code: "ja", name: "日本語", source: include_str!("ja.tsv"), plural: plural_none, rtl: false, catalog: OnceLock::new() },
     // Simplified Chinese; `zh`, `zh-CN`, `zh-SG` and `zh-Hans-*` locales resolve here (see `candidates`).
@@ -210,6 +210,8 @@ pub static LANGUAGES: [LangInfo; 23] = [
     // Vietnamese; every `vi-*` locale (`vi-VN`, `vi_VN.UTF-8`) resolves here. CLDR `vi` counts have
     // one form ("other"), so `@plural` entries list a single form.
     LangInfo { code: "vi", name: "Tiếng Việt", source: include_str!("vi.tsv"), plural: plural_none, rtl: false, catalog: OnceLock::new() },
+    // Thai; every `th-*` locale (`th-TH`, `th_TH.UTF-8`) resolves here. No grammatical plural.
+    LangInfo { code: "th", name: "ไทย", source: include_str!("th.tsv"), plural: plural_none, rtl: false, catalog: OnceLock::new() },
 ];
 
 impl LangInfo {