[KeyffMS]

R2h

Small move-only continuation of #83 R2.

Scope:

• move ApplicationEffectError, EffectRunner, and ApplicationRuntime from crates/lantern-app/src/application.rs into crates/lantern-app/src/application/runtime.rs;
• preserve the existing public surface through re-export from application.rs;
• keep public ApplicationAction / ApplicationEffect, exactly one ApplicationState, and the top-level ApplicationState::reduce in application.rs.

Safety/architecture:

• no behavior or public API narrowing intended;
• write confirmation and restore confirmation remain unchanged in application.rs, so the existing exact-confirmation architecture gate continues to cover them directly;
• no scheduler/budget/fairness/QueueFull changes;
• no write/restore/session authority changes and no conformance/gate weakening.

Refs #83