v0.2.3-beta

Added

• opt_level optimization tiers (spec §10.2/§13.2, Phase 8). A new OptLevel policy (O0–O3, default O2) gates the compiler optimization channels: the arithmetic-series loop closed form now requires opt_level >= O1, automatic JIT hot-path compilation and tail-call optimization require opt_level >= O2, and tier O3 enables SIMD vectorization of dense F64 array elementwise binary ops (runtime::simd, via the portable wide crate on stable Rust). simplify_level was wired into the symbolic simplify pipeline (simplify_at), so lowering it reduces only how deeply a symbolic value is canonicalized — never its mathematical value. Results are semantically identical across tiers (equivalence tests; IEEE lane arithmetic is bit-identical to scalar).

Changed

• @builtin layered optimization (spec §18.4, Phase 9). @builtin may now take a tier, @builtin(O0)–@builtin(O3): tier O0 (bare) stays signature-only and must bind to a registered Rust implementation (E0055/E0056); tiers O1–O3 carry a .pra fallback body (the semantic authority, E0056 if absent) plus an optional Rust fast path used when opt_level >= N, with an invalid tier reported as E0057. A new Function::Layered variant dispatches between the two implementations at call time. register_impl was augmented with register_impl_level and a declarative builtin! macro (builtin!("num::fibonacci", fibonacci_impl, O1)) that replaces the manual string-keyed registration calls across the stdlib crates; the .pra @builtin(ON) annotation remains the authoritative dispatch tier.