OpenJO: fix Traditional Chinese rendering and runtime language switching

[hsz0566]

Fixes #1196

OpenJO submission draft

Suggested recipient: OpenJK maintainers / JACoders
Suggested subject: [PATCH] OpenJO: use sp_language for JK2 Asian character decoding

Hello OpenJK maintainers,

I would like to submit a fix for the OpenJO Traditional Chinese rendering issue
reported in:

#1196

OpenJO correctly uses the numeric sp_language cvar to select Jedi Outcast
STRIP entries. For example, sp_language 5 selects TEXT_LANGUAGE6.
The renderer also has a JK2-specific language enum mapping, but the JK2 branch
of AnyLanguage_ReadCharFromString() still calls the JKA
Language_IsKorean/Taiwanese/Japanese() helpers from
stringed_ingame.h. Those helpers inspect se_language, which normally
remains english in OpenJO.

As a result, valid Big5 text is loaded from the STRIP files but each two-byte
Chinese character is interpreted as two Western characters. This produces the
garbled menu and subtitle output shown in issue #1196.

The attached patch:

1. Makes the JK2 character decoder use GetLanguageEnum(), which is backed by
   sp_language.
2. Makes the JK2 enum mapping return Western for unsupported or unset values,
   avoiding stale Asian state after a language change.
3. Makes the JK2 UI call JK2SP_CheckForLanguageUpdates() after an in-game
   sp_language change, keeping STRIP reloads synchronized with renderer
   decoding.

Validation performed:

• Reproduced the issue with the official OpenJO Windows x86_64 build from
  OpenJK commit 1a6a6434.
• Confirmed sp_language 5 selected TEXT_LANGUAGE6.
• Confirmed all four Taiwanese font pages,
  fonts/tai_16_1024_0 through _3, loaded with valid shader handles.
• Validated 2,238 supplied Traditional Chinese STRIP entries as Big5 with zero
  invalid entries.
• Built and linked the patched OpenJO renderer successfully.
• Built the equivalent revised JKXR Android application successfully.
• The first Quest 3 test confirmed correct Traditional Chinese rendering and
  exposed the separate live-switching issue addressed by item 3 above.
• git diff --check and forward/reverse git apply --check pass.
• The changes are contained inside the JK2-specific path and do not alter the
  Jedi Academy language path.

One limitation: final visual testing of the locally rebuilt Windows DLL was
blocked by this machine's Windows Application Control policy
(0xc0e90002) because the generated DLL is unsigned. No security setting was
disabled. The unpatched official build and the diagnostic build were both
tested against the same game data. The revised live-switch behavior still
needs a final runtime regression test.

The source patch is attached as:

0001-openjo-use-sp-language-for-jk2-asian-fonts.patch

Thank you for reviewing this fix.

Best regards,
Song / hsz0566