feedback5: merge W5I — real i18n phase 1: shared/i18n.js (Chinese msgids, params, data names), English game texts from the official EN client data (data/i18n/en.json), the 中文 / English switch on the title screen and in 设置, title / lobby / room / settings converted, server toasts and ticker lines with msgid + params, tools/i18n.mjs, docs/I18N.md (PR #70's translations by @YuriRestia reused, credited)

Conflict: server/match/player/basics.js imports (W5G's checkNotOwned + W5I's msg / dn). data/i18n/en.json rebuilt on the merged data (tools/build-i18n.mjs --offline): the 自选 data adds texts of CN-only operators and modules the EN client lacks, so coverage is 97.6 % (skills 95.9, talents 95.1); the coverage floors in test/i18n-data.test.js and docs/I18N.md say so. Golden unchanged; i18n / lobby / match / ui suites 1144/1144 after the rebuild, i18n e2e 1/1.

docs/PLAYING.md

@@ -4,6 +4,8 @@
 
 本文数值来自官方数据表（`data/config.json` 等）与 [research](research/00-INDEX.md)；游戏内左下角 📖「玩法说明」有官方教程图（随素材一起下载；没下载到时显示文字要点）。操作方式见 [README · 操作](../README.md#操作)。
 
+界面语言：默认中文；标题画面右上角或「设置」里可切换 **中文 / English**（会记住选择，不用刷新）。英文的干员、技能、盟约、装备、敌人等游戏文本取自官方英文服数据；尚未翻译的界面文字暂时显示中文（docs/I18N.md）。
+
 ## 1. 一局的流程
 
 ```