Fix Android black screens from locale parsing and font substitution failures

[SocialHummingbird]

Summary

• Adapts the Android locale fix path from Fix black screen caused by Unicode locale extensions #38 so CultureInfo does not receive Unicode extension locale tails.
• Sanitizes locale output at NullPlatformUtilStrategy.GetRawLanguage via postfix, preserving the game�s original GetThreeLetterLanguageCode logic for script/region-specific handling.
• Handles both -u-... and -#u-... extension forms, with en-US fallback when the sanitized raw locale is empty or whitespace.
• Adds a guarded font-substitution workaround from Fix post-update blackscreen: swallow font NRE, unbreak ModLoaderPatches #49 for post-update Android startup/UI black-screen failures.
• Patches all ApplyLocaleFontSubstitution overloads to avoid AmbiguousMatchException if the game DLL exposes multiple matching methods.
• Suppresses only NullReferenceException in ApplyLocaleFontSubstitution; non-NRE exceptions remain visible.
• Scope intentionally limited to startup black-screen paths. No unrelated launcher, ModLoader, controller, or feature changes.

Links

• Builds on Fix black screen caused by Unicode locale extensions #38
• Adapts black-screen portion of Fix post-update blackscreen: swallow font NRE, unbreak ModLoaderPatches #49
• Related symptom threads: Black screen #11 and Doesn't run on Pixel 9 #27

Validation status

• Local dotnet build src/STS2Mobile/STS2Mobile.csproj was attempted.
• Build is blocked in this checkout because referenced assemblies are missing under upstream/godot-export/.godot/mono/publish/arm64/: 0Harmony, GodotSharp, and sts2.
• Maintainer/device runtime validation is requested, especially on Samsung Fold and Android 16 locale-extension repro devices.

Test plan

• Build src/STS2Mobile/STS2Mobile.csproj in a checkout with the required Godot/StS2 reference assemblies
• Samsung Fold repro settings: verify Play no longer leaves persistent dev/command overlay or black screen
• Samsung Android 16 / One UI non-US locale path
• Pixel Android 16 locale extension path (-u-... / -#u-...)
• Default English US locale/regional preferences regression check
• Confirm no CultureNotFoundException at startup
• Confirm no repeated ApplyLocaleFontSubstitution NRE spam

[SocialHummingbird]

Update for 1a4b6208bb1c72aacaebc0baae5760c81692a67a:

• Font substitution patch now enumerates and patches all ApplyLocaleFontSubstitution overloads, avoiding AmbiguousMatchException if the game DLL exposes more than one matching method.
• Locale fix now sanitizes NullPlatformUtilStrategy.GetRawLanguage via postfix instead of replacing GetThreeLetterLanguageCode, so the game�s original script/region language-code handling still runs.
• Locale sanitizer still handles both -u-... and -#u-...; empty/whitespace sanitized raw locales fall back to en-US before downstream parsing.

Build was attempted locally, but this checkout is missing the referenced 0Harmony, GodotSharp, and sts2 assemblies under upstream/godot-export/.godot/mono/publish/arm64/, so maintainer/device validation is still needed.

[SocialHummingbird]

Quick follow-up on #60: this combines the locale and font-substitution startup fixes discussed in #38/#49, with additional edge-case hardening.