[client] transport: introduce pluggable frame transports

Move shared-memory ownership, LGMP session handling, queue access, and
DMA setup behind a transport interface. The LGMP backend preserves the
existing zero-copy frame and DMA paths while owning its lgmp:* options.

Expose the initialized EGL context through a versioned renderer interop
record for future accelerated decode backends. Add an LGMP-independent,
deterministic test transport for graphics-pipeline validation.

client/transports/CMakeLists.txt

@@ -0,0 +1,44 @@
+cmake_minimum_required(VERSION 3.10)
+project(transports LANGUAGES C)
+
+set(TRANSPORT_H "${CMAKE_BINARY_DIR}/include/dynamic/transports.h")
+set(TRANSPORT_C "${CMAKE_BINARY_DIR}/src/transports.c")
+
+file(WRITE  ${TRANSPORT_H} "#include \"interface/transport.h\"\n\n")
+file(APPEND ${TRANSPORT_H} "extern const LG_TransportOps * LG_Transports[];\n\n")
+
+file(WRITE  ${TRANSPORT_C} "#include \"interface/transport.h\"\n\n")
+file(APPEND ${TRANSPORT_C} "#include <stddef.h>\n\n")
+
+set(TRANSPORTS "_")
+set(TRANSPORTS_LINK "_")
+function(add_transport name)
+  set(TRANSPORTS      "${TRANSPORTS};${name}" PARENT_SCOPE)
+  set(TRANSPORTS_LINK "${TRANSPORTS_LINK};transport_${name}" PARENT_SCOPE)
+  add_subdirectory(${name})
+endfunction()
+
+# Add/remove transports here!
+add_transport(LGMP)
+if(ENABLE_TEST_TRANSPORT)
+  add_transport(Test)
+endif()
+
+list(REMOVE_AT TRANSPORTS      0)
+list(REMOVE_AT TRANSPORTS_LINK 0)
+
+list(LENGTH TRANSPORTS TRANSPORT_COUNT)
+file(APPEND ${TRANSPORT_H} "#define LG_TRANSPORT_COUNT ${TRANSPORT_COUNT}\n")
+
+foreach(transport ${TRANSPORTS})
+  file(APPEND ${TRANSPORT_C} "extern const LG_TransportOps LGT_${transport};\n")
+endforeach()
+
+file(APPEND ${TRANSPORT_C} "\nconst LG_TransportOps * LG_Transports[] =\n{\n")
+foreach(transport ${TRANSPORTS})
+  file(APPEND ${TRANSPORT_C} "  &LGT_${transport},\n")
+endforeach()
+file(APPEND ${TRANSPORT_C} "  NULL\n};")
+
+add_library(transports STATIC ${TRANSPORT_C})
+target_link_libraries(transports ${TRANSPORTS_LINK})