feat(motion): add GEM-X backend and duplex streaming API

Add the GEM-X native backend with live pose and root displacement output, bounded duplex WebSocket streaming, session authorization, metrics and usage accounting. Share the embedded bidirectional RPC channel adapter across streaming backends.

Include backend build and gallery integration, API documentation, schemas and tests.

Assisted-by: Codex:gpt-6
Signed-off-by: Richard Palethorpe <io@richiejp.com>
(cherry picked from commit 016dc3d71a)

.github/workflows/bump_deps.yaml

@@ -94,6 +94,10 @@ jobs:
             variable: "KIMODO_VERSION"
             branch: "main"
             file: "backend/go/kimodocpp/Makefile"
+          - repository: "localai-org/gem-x.cpp"
+            variable: "GEMX_VERSION"
+            branch: "main"
+            file: "backend/go/gemxcpp/Makefile"
           - repository: "mudler/go-piper"
             variable: "PIPER_VERSION"
             branch: "master"