[KeyffMS]

R2k

Small move-only continuation of #83 R2.

Scope:

• move public ApplicationAction and ApplicationEffect definitions from application.rs into the existing application/runtime.rs;
• preserve the existing public API through re-export from application.rs;
• keep exactly one public ApplicationState definition and the top-level ApplicationState::reduce in application.rs.

Safety/architecture:

• no reducer logic or behavior changed;
• write/restore exact operator-confirmation comparisons remain unchanged in application.rs and directly covered by the existing architecture gate;
• no session/write authority, scheduler/budget/fairness/QueueFull, filesystem boundary, or conformance semantics changed;
• no gate/test weakening.

Refs #83