feat(backend): rfdetr-cpp native object detection + segmentation backend (#10028)

Adds a Go native gRPC backend that dlopens librfdetrcpp.so (built from
mudler/rf-detr.cpp at the pinned RFDETR_VERSION) via purego and exposes
the rfdetr.cpp inference pipeline through LocalAI's existing Detect RPC.

Supports all 5 RF-DETR detection variants (Nano/Small/Base/Medium/Large)
and 6 segmentation variants (SegNano/SegSmall/SegMedium/SegLarge/
SegXLarge/Seg2XLarge) with F32/F16/Q8_0/Q4_K quantizations. Pre-built
GGUFs ship at mudler/rfdetr-cpp-* on HuggingFace.

Detection returns Bbox + class_name + confidence; segmentation also
returns PNG-encoded per-detection masks via the rfdetr_capi accessor
functions (rfdetr_capi_get_detection_{class_id,box,score,class_name,
mask_png}).

End-to-end verified through POST /v1/detection: HTTP -> gRPC -> purego
dlopen -> rfdetr.cpp -> ggml -> response (9 detections on the detection
model, 21 detections + valid PNG masks on the seg-nano model against
the kitchen fixture).

Wiring:
  - backend/go/rfdetr-cpp/{main.go,gorfdetrcpp.go,CMakeLists.txt,
    Makefile,run.sh,package.sh,test.sh,.gitignore}
  - Top-level Makefile: BACKEND_RFDETR_CPP, docker-build target,
    .NOTPARALLEL, prepare-test-extra, test-extra
  - backend/go/rfdetr-cpp/Makefile: `test` target invoked by test-extra
  - .github/backend-matrix.yml: CPU + CUDA-12/13 + L4T CUDA-12/13
    (arm64) + HIP + Vulkan (amd64 + arm64) + SYCL f32/f16
  - backend/index.yaml: rfdetr-cpp meta anchor + latest/development
    image entries for every matrix tag-suffix
  - .github/workflows/bump_deps.yaml: RFDETR_VERSION pin tracking
    (mudler/rf-detr.cpp branch main)
  - gallery/index.yaml: 11 rfdetr-cpp-* entries (nano + 4 detection
    variants + 6 seg variants), all backed by mudler/rfdetr-cpp-*
    on HuggingFace with sha256 pinning on the F16 default
  - core/gallery/importers/rfdetr.go: GGUF auto-routing for HF imports
    (mudler/rfdetr-cpp-* repos route to rfdetr-cpp, Transformer-format
    repos stay on the Python rfdetr backend; explicit preferences.backend
    overrides both heuristics)
  - core/gallery/importers/rfdetr_test.go: table-driven coverage of the
    auto-routing + a live mudler/rfdetr-cpp-nano cross-check

scripts/changed-backends.js needs no change: the existing
Dockerfile.golang -> backend/go/${item.backend}/ branch already routes
the 9 rfdetr-cpp matrix entries to the correct backend path.

Assisted-by: Claude:claude-opus-4-7 [Claude Code]

Signed-off-by: Ettore Di Giacinto <mudler@localai.io>
Co-authored-by: Ettore Di Giacinto <mudler@localai.io>

.github/workflows/bump_deps.yaml

@@ -50,6 +50,10 @@ jobs:
             variable: "SAM3_VERSION"
             branch: "main"
             file: "backend/go/sam3-cpp/Makefile"
+          - repository: "mudler/rf-detr.cpp"
+            variable: "RFDETR_VERSION"
+            branch: "main"
+            file: "backend/go/rfdetr-cpp/Makefile"
           - repository: "predict-woo/qwen3-tts.cpp"
             variable: "QWEN3TTS_CPP_VERSION"
             branch: "main"

.github/workflows/test-extra.yml

@@ -37,6 +37,7 @@ jobs:
       sglang: ${{ steps.detect.outputs.sglang }}
       acestep-cpp: ${{ steps.detect.outputs.acestep-cpp }}
       qwen3-tts-cpp: ${{ steps.detect.outputs.qwen3-tts-cpp }}
+      rfdetr-cpp: ${{ steps.detect.outputs.rfdetr-cpp }}
       vibevoice-cpp: ${{ steps.detect.outputs.vibevoice-cpp }}
       localvqe: ${{ steps.detect.outputs.localvqe }}
       voxtral: ${{ steps.detect.outputs.voxtral }}
@@ -843,6 +844,42 @@ jobs:
       - name: Test qwen3-tts-cpp
         run: |
           make --jobs=5 --output-sync=target -C backend/go/qwen3-tts-cpp test
+  # Per-backend smoke for rfdetr-cpp: builds the .so + Go binary and runs
+  # `make -C backend/go/rfdetr-cpp test`. test.sh fetches the small (~20 MB)
+  # rfdetr-nano-q8_0 GGUF from the published mudler/rfdetr-cpp-nano HF repo
+  # via curl and synthesises a tiny PNG to exercise the wire protocol.
+  tests-rfdetr-cpp:
+    needs: detect-changes
+    if: needs.detect-changes.outputs.rfdetr-cpp == 'true' || needs.detect-changes.outputs.run-all == 'true'
+    runs-on: ubuntu-latest
+    steps:
+      - name: Clone
+        uses: actions/checkout@v6
+        with:
+          submodules: true
+      - name: Dependencies
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y build-essential cmake curl libopenblas-dev
+      - name: Setup Go
+        uses: actions/setup-go@v5
+      - name: Display Go version
+        run: go version
+      - name: Proto Dependencies
+        run: |
+          # Install protoc
+          curl -L -s https://github.com/protocolbuffers/protobuf/releases/download/v26.1/protoc-26.1-linux-x86_64.zip -o protoc.zip && \
+          unzip -j -d /usr/local/bin protoc.zip bin/protoc && \
+          rm protoc.zip
+          go install google.golang.org/protobuf/cmd/protoc-gen-go@v1.34.2
+          go install google.golang.org/grpc/cmd/protoc-gen-go-grpc@1958fcbe2ca8bd93af633f11e97d44e567e945af
+          PATH="$PATH:$HOME/go/bin" make protogen-go
+      - name: Build rfdetr-cpp
+        run: |
+          make --jobs=5 --output-sync=target -C backend/go/rfdetr-cpp
+      - name: Test rfdetr-cpp
+        run: |
+          make --jobs=5 --output-sync=target -C backend/go/rfdetr-cpp test
   # Per-backend smoke for vibevoice-cpp: builds the .so + Go binary and
   # runs `make -C backend/go/vibevoice-cpp test`. test.sh auto-downloads
   # the published mudler/vibevoice.cpp-models bundle (TTS Q8_0 + ASR Q4_K