feat(runtime): add resident Wasmtime actor runtime

- define versioned service and clock WIT contracts
- enforce import allowlists, fuel, epoch, memory, I/O, and mailbox limits
- keep one Store and Component Instance resident per serial Actor
- add echo, counter, fault, spin, and capability probe components
- cover lifecycle, concurrency, sandbox, and fault recovery behavior

crates/wasmeld-runtime/src/lib.rs

@@ -0,0 +1,16 @@
+//! A minimal resident WebAssembly Component runtime.
+//!
+//! The runtime intentionally has no network protocol or business capabilities.
+//! It provides a restricted WASI compatibility context, links explicitly
+//! imported host capabilities, loads a Component that implements the stable
+//! service exports, and invokes it through one serial Actor.
+
+mod bindings;
+mod error;
+mod manifest;
+mod runtime;
+
+pub use error::RuntimeError;
+pub use manifest::{ResourceLimits, ServiceKey, ServiceManifest};
+pub use runtime::{ActorHandle, Runtime, RuntimeConfig, RuntimeStats};
+pub use wasmeld_package::SERVICE_WORLD;