docs(cgo): add agent-oriented package usage examples

Co-Authored-By: Virgil <virgil@lethean.io>

doc.go

@@ -0,0 +1,23 @@
+// Package cgo is a focused harness for safe Go-to-C interop helpers.
+//
+// Common usage:
+//
+//	buffer := NewBuffer(32)
+//	n := buffer.CopyFrom([]byte("agent"))
+//	defer buffer.Free()
+//
+//	err := Call(unsafe.Pointer(C.some_function), buffer.Ptr(), SizeT(n))
+//	if err != nil {
+//		// handle mapped C errno
+//	}
+//
+//	scope := NewScope()
+//	defer scope.Close()
+//	cString := scope.CString("hello")
+//	buffer := scope.Buffer(16)
+//
+//	if err := Call(unsafe.Pointer(C.another_function), cString, buffer.Ptr()); err != nil {
+//		// scope.Close() will release C string + buffer
+//	}
+package cgo
+