Add a Traditional Chinese text language (--lang zh-TW) - #422

RO3Emu turns the Simplified Chinese strings the client draws into English. With a Traditional Chinese client that leaves a mix of Traditional Chinese (the client's own) and English, and there is no way to ask for Chinese instead. This adds a second language for the in-game text map.

RO3Emu.exe --lang zh-TW:

• pairs Localization_zh_CN with the client's own Localization_zh_TW from the player's game folder (the publisher's Taiwan wording), the same way the English map pairs it with Localization_en. Nothing from the client is committed;
• fills what that table lacks from src/Ro3Emu.Setup/translations-zhtw/*.tsv (2,010 rows, same zh<TAB>text format as the English files). Those rows never replace a pair from the client's table. They were drafted from an automatic Simplified-to-Taiwan conversion and corrected against the wording of the client's own zh_TW pairs; text marked （无需翻译） (designer and test strings) is left out;
• English stays the default. --lang is remembered in RO3Emu.settings.json. The generated map records its language in its first line (the # zh en - generated by prefix is unchanged, so ClientPatcher still recognises it), and start/host/join rebuild it once when the language changed. After an export the map is only rebuilt for a language change.

A user who never passes --lang gets the same map, the same export and the same failure rules as before: the zh_TW chunk is an export table only in zh-TW mode.

Why the translations are in src/Ro3Emu.Setup and not next to the English ones in src/Ro3Emu.Loc: that folder is part of the stamp of prebuilt/client (tools/release/client-stamp.ps1), and these texts are not in those DLLs, so adding them there would force a DLL refresh for nothing.

Checked:

• dotnet test tests/Ro3Emu.Setup.Tests: 157 passed, 9 skipped. New tests cover the zh_TW pairing, the stored language, the --lang values and the shape of the embedded translations.
• dotnet format whitespace, tools/AnalyzerBaseline (CA1861 baseline 100 -> 99, the count went down), the server build, and the prebuilt/client stamp (this PR touches nothing the stamp covers).
• RO3Emu.exe export <game> <data> --lang zh-TW on a real release 140083 client: 27,276 texts in 36 s.

Known limits:

• Exact strings work. Strings the client composes at run time (a template with a number, or text with a Chinese name inside) are mapped by Ro3Loc in the client DLL, which only accepts a result without Chinese in it. In zh-TW mode those stay as the client draws them. Fixing that is a small change in src/Ro3Emu.Loc/Ro3Loc.cs, but it needs the prebuilt DLLs rebuilt, and my build of the current sources does not reproduce the committed DLL bytes, so I left it out. I can send it as a follow-up, with prebuilt/client rebuilt on your side.
• I have not looked at the running game yet, hence the draft.
• The web panel (admin pages) is English only; that would be a separate change.