Better rules required for netplay

RetroAchievements currently has a bit of a "blind spot" when it comes to netplay.

Picture the following: 2 users initiate a netplay session for Super Mario 64. Player 2 is logged in to RetroAchievements. They (player 2) are not playing. Super Mario 64 is a one-player game. rcheevos has no idea this is a netplay session, or whether the local player is player 1 or player 2. rcheevos just sees stars being collected on both machines.

Therefore, player 2 will start earning achievements, even though they are not playing; they are simply spectating.

My suggestion:

• For hardcore, emulators should need to indicate to rcheevos/RA API that the session is a netplay session.
• In hardcore, if it is a netplay session, achievements should only be earned on subsets that have been marked as "netplay approved" (for example, the Mario Kart 64 Multiplayer Subset).

No files, tests, or entry points are identified. Start by clarifying how emulators should signal netplay sessions, how rcheevos or the RA API would consume that signal, and where "netplay approved" subsets are defined. Done requires an agreed, documented rule set and implementation scope.