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/Cargo.toml

@@ -0,0 +1,16 @@
+[package]
+name = "wasmeld-runtime"
+version = "0.1.0"
+edition.workspace = true
+rust-version.workspace = true
+license.workspace = true
+
+[dependencies]
+serde.workspace = true
+thiserror.workspace = true
+toml.workspace = true
+wasmeld-package = { path = "../wasmeld-package" }
+wasmtime.workspace = true
+wasmtime-wasi.workspace = true
+
+[dev-dependencies]