Track RetroArch Android host-override integration

[misantronic]

Track follow-up work for RetroArch Android support now that the upstream PR is open.

Upstream PR:

• Android: add RetroAchievements host override receiver libretro/RetroArch#19093

Why:

• RetroArch now has a working Android broadcast path for setting and clearing the RetroAchievements host override
• RAOfflineProxy should track upstream review/merge status and align its RetroArch integration around that mechanism

Follow-up items:

• monitor upstream feedback and required PR changes
• confirm the final broadcast contract once the upstream API settles
• keep RAOfflineProxy RetroArch integration preferring the broadcast path instead of direct retroarch.cfg patching where supported
• keep the existing retroarch.cfg fallback for stock RetroArch builds without receiver support
• re-test set and clear flows against the merged upstream build
• document package/action details for release and debug builds if needed

Notes:

• device testing confirmed the set/apply path works and routes traffic through the proxy
• clear/reset also works and restores the prior hardcore preference
• local build-only changes for Android toolchain compatibility were intentionally kept out of the upstream PR

[misantronic]

Closing in favor of #33, which now tracks Android host-override integration status across emulators in one place.