ic-core — foundational types for IronCrypto

Zero-dependency, no_std-first building blocks shared by every other crate in the workspace:

• [Error] / [Result] — a single, exhaustive, non-panicking error domain.
• [ct] — constant-time comparison and selection primitives.
• [Zeroizing] — scope-bound secret erasure with a compiler-fence barrier.
• [traits] — the object-safe algorithm contracts (Digest, Mac, Aead, …).
• [codec] — hex / base64 encoding used by the agent-facing surfaces.
• [cpu] — CPU feature detection, shared by the backends and the ontology.
• [entropy] — OS entropy acquisition (SP 800-90B conditioned input).

Every public function in this crate is total: it returns Result rather than panicking, so an autonomous agent can drive the library without tripping an abort in a sandbox.