feat(runtime): modularize host capabilities

- add an exact-version Capability Registry and structured descriptors
- move Clock bindings, host state, and Linker installation into its own module
- derive required capabilities from Component imports and link only requested interfaces
- cover exact-version resolution and minimal per-component capability sets

crates/wasmeld-runtime/src/bindings.rs

@@ -5,12 +5,3 @@ wasmtime::component::bindgen!({
     path: "../../wit/service",
     world: "service-component",
 });
-
-pub(crate) mod clock {
-    // Host capabilities are generated separately so adding a capability does
-    // not expand the baseline service contract for every component.
-    wasmtime::component::bindgen!({
-        path: "../../wit/clock",
-        world: "clock-host",
-    });
-}