v0.3.1

Changed

• Eff type alias renamed to Effectful — the Eff<'a, Effs, R, L> type alias for an unhandled Program has been renamed to Effectful<'a, Effs, R, L> for clarity.
  The #[effectful] macro now generates Effectful<...> as its return type.
• unsafe { unreachable_unchecked() } replaced with debug-checked macro — all internal uses of core::hint::unreachable_unchecked() are now wrapped in a
  debug_unreachable! macro that panics with a descriptive message in debug builds, while preserving the optimization hint in release builds. This makes invariant violations
  easier to diagnose during development.

Removed

• declare_effect! macro removed — use the #[effect(ResumeType)] attribute macro instead, which supports all the same features (lifetimes, generics, named fields, GAT
  resume types) plus visibility modifiers, multiple trait bounds, #[derive(...)], and arbitrary attributes.
  EOF