[repos] lgprotocol: import shared protocol definitions

Add LGProtocol as a pinned submodule and consume its KVMFR protocol
definitions throughout the client, host, IDD, OBS, and profiler.

Keep Looking Glass framebuffer helpers local while removing duplicated
protocol headers and migrating users to KVMFR-scoped types.

common/CMakeLists.txt

@@ -15,6 +15,19 @@ if (CMAKE_C_COMPILER_ID STREQUAL "Clang")
   )
 endif()
 
+function(_lg_common_add_protocol)
+  # Function scope preserves the parent BUILD_TESTING setting while disabling
+  # LGProtocol's standalone tests in the nested build.
+  set(BUILD_TESTING OFF)
+  add_subdirectory(
+    "${CMAKE_CURRENT_SOURCE_DIR}/../repos/LGProtocol"
+    "${CMAKE_CURRENT_BINARY_DIR}/LGProtocol"
+    EXCLUDE_FROM_ALL
+  )
+endfunction()
+
+_lg_common_add_protocol()
+
 add_subdirectory(src/platform)
 
 set(COMMON_SOURCES
@@ -35,7 +48,11 @@ set(COMMON_SOURCES
 )
 
 add_library(lg_common STATIC ${COMMON_SOURCES})
-target_link_libraries(lg_common lg_common_platform)
+target_link_libraries(lg_common
+  PUBLIC
+    lg_common_platform
+    LGProtocol::LGProtocol
+)
 
 if(ENABLE_BACKTRACE)
   target_compile_definitions(lg_common PUBLIC -DENABLE_BACKTRACE)