Split interactions tests into 6 parts for MSVC heap exhaustion fix

- Change from 3-way split (~1900 lines) to 6-way split (~750-825 lines)
- Extract all helper functions into interactions_helpers.hpp
- Remove monolithic interactions.cpp in favor of split parts
- Each part contains ~27-28 tests
- All 164 tests pass on Windows with smaller compilation units

Author: 0xeb

CMakeLists.txt

@@ -233,7 +233,7 @@ if(FASTMCPP_BUILD_TESTS)
   target_link_libraries(fastmcpp_server_patterns PRIVATE fastmcpp_core)
   add_test(NAME fastmcpp_server_patterns COMMAND fastmcpp_server_patterns)
 
-  # Server interactions split into 3 parts to avoid MSVC heap exhaustion
+  # Server interactions split into 6 parts to avoid MSVC heap exhaustion
   add_executable(fastmcpp_server_interactions_p1 tests/server/interactions_p1.cpp)
   target_link_libraries(fastmcpp_server_interactions_p1 PRIVATE fastmcpp_core)
   add_test(NAME fastmcpp_server_interactions_p1 COMMAND fastmcpp_server_interactions_p1)
@@ -246,6 +246,18 @@ if(FASTMCPP_BUILD_TESTS)
   target_link_libraries(fastmcpp_server_interactions_p3 PRIVATE fastmcpp_core)
   add_test(NAME fastmcpp_server_interactions_p3 COMMAND fastmcpp_server_interactions_p3)
 
+  add_executable(fastmcpp_server_interactions_p4 tests/server/interactions_p4.cpp)
+  target_link_libraries(fastmcpp_server_interactions_p4 PRIVATE fastmcpp_core)
+  add_test(NAME fastmcpp_server_interactions_p4 COMMAND fastmcpp_server_interactions_p4)
+
+  add_executable(fastmcpp_server_interactions_p5 tests/server/interactions_p5.cpp)
+  target_link_libraries(fastmcpp_server_interactions_p5 PRIVATE fastmcpp_core)
+  add_test(NAME fastmcpp_server_interactions_p5 COMMAND fastmcpp_server_interactions_p5)
+
+  add_executable(fastmcpp_server_interactions_p6 tests/server/interactions_p6.cpp)
+  target_link_libraries(fastmcpp_server_interactions_p6 PRIVATE fastmcpp_core)
+  add_test(NAME fastmcpp_server_interactions_p6 COMMAND fastmcpp_server_interactions_p6)
+
   add_executable(fastmcpp_server_context_meta tests/server/context_meta.cpp)
   target_link_libraries(fastmcpp_server_context_meta PRIVATE fastmcpp_core)
   add_test(NAME fastmcpp_server_context_meta COMMAND fastmcpp_server_context_meta)