Where should the offline-progress cap live?

[mnichols08]

When the player returns after being away, Rustbound converts elapsed time into idle damage. Right now that elapsed time has no design cap.

Suppose we decide that only the first eight hours away should count. Which layer should own that rule?

1. Rust engine: the cap is game balance and should behave the same in every future interface.
2. Browser component: the browser owns the clock, so it should clamp elapsed time before calling Rust.
3. Both: the browser offers friendly behavior, while Rust enforces the invariant.
4. No cap: unlimited offline progress is part of the game's identity.

Consider cheating, testability, save compatibility, future non-browser clients, and what feels fair to a player. There is no implementation attached to this Discussion yet; the goal is to agree on the rule and its owner before opening an issue.