fix(registry): log Unregister Close errors, add doc comments and 59 unit tests

Log close errors in Unregister instead of silently discarding them.
Add doc comments to all exported symbols across 20 registry files.
Add comprehensive tests covering base registry, all wrapper types,
hot-reload delegation, nil-fallback semantics, and global accessors.

registry/admission.go

@@ -6,14 +6,19 @@ import (
 	"github.com/go-gost/core/admission"
 )
 
+// admissionRegistry implements a hot-reload-safe registry for admission.Admission.
+// The Get method returns a wrapper that looks up the current value on every call.
 type admissionRegistry struct {
 	registry[admission.Admission]
 }
 
+// Register stores an Admission under the given name.
 func (r *admissionRegistry) Register(name string, v admission.Admission) error {
 	return r.registry.Register(name, v)
 }
 
+// Get returns a wrapper that delegates to the currently registered Admission.
+// Returns nil if name is empty.
 func (r *admissionRegistry) Get(name string) admission.Admission {
 	if name != "" {
 		return &admissionWrapper{name: name, r: r}