Refactor to use gopher::orch::core namespace (#3)

Add gopher as top-level namespace for all gopher-orch source code.
This provides clearer namespace hierarchy and avoids potential
conflicts with other libraries.

Namespace structure: gopher::orch::core

Author: gophergogo

examples/hello_world/main.cpp

@@ -5,7 +5,7 @@
 #include "orch/core/hello.h"
 #include "orch/core/version.h"
 
-using namespace orch::core;
+using namespace gopher::orch::core;
 
 int main(int argc, char* argv[]) {
   std::cout << "gopher-orch version: " << Version::string() << std::endl;

examples/mcp_client/mcp_client_example.cc

@@ -21,7 +21,7 @@
 #include "mcp/json/json_bridge.h"
 #include "mcp/types.h"
 
-using namespace orch::core;
+using namespace gopher::orch::core;
 using namespace mcp;
 
 int main(int argc, char* argv[]) {

include/orch/core/hello.h

@@ -3,6 +3,7 @@
 #include <memory>
 #include <string>
 
+namespace gopher {
 namespace orch {
 namespace core {
 
@@ -42,3 +43,4 @@ class HelloBuilder {
 
 }  // namespace core
 }  // namespace orch
+}  // namespace gopher

include/orch/core/version.h

@@ -6,6 +6,7 @@
 
 #define GOPHER_ORCH_VERSION_STRING "0.1.0"
 
+namespace gopher {
 namespace orch {
 namespace core {
 
@@ -18,3 +19,4 @@ struct Version {
 
 }  // namespace core
 }  // namespace orch
+}  // namespace gopher

src/orch/hello.cpp

@@ -4,6 +4,7 @@
 
 #include "orch/core/version.h"
 
+namespace gopher {
 namespace orch {
 namespace core {
 
@@ -55,3 +56,4 @@ std::unique_ptr<Hello> HelloBuilder::build() const {
 
 }  // namespace core
 }  // namespace orch
+}  // namespace gopher

tests/orch/hello_test.cpp

@@ -5,7 +5,7 @@
 
 #include "orch/core/version.h"
 
-using namespace orch::core;
+using namespace gopher::orch::core;
 using namespace testing;
 
 class HelloTest : public ::testing::Test {