feat(backend): locate-anything-cpp (open-vocabulary object detection via ggml)

[localai-bot]

What

Adds a new LocalAI backend locate-anything-cpp for open-vocabulary object detection (visual grounding): given an image and a free-text prompt, it returns labeled boxes. It wraps locate-anything.cpp - a C++/ggml port of NVIDIA's LocateAnything-3B - via its flat C ABI.

Same family as the existing detection backends: it mirrors backend/go/rfdetr-cpp/ almost exactly (Go + purego Dlopen, no cgo; a CMake MODULE lib static-links ggml into a per-CPU-variant .so) and implements the gRPC Detect RPC. Open-vocab means it consumes DetectOptions.prompt (the same field SAM3 uses).

How it maps

• Detect(DetectOptions{Src, Prompt}) -> base64 image to temp file -> la_capi_locate_path(ctx, img, prompt, hybrid) -> DetectResponse{ Detection{X, Y, Width, Height, Confidence=1.0, ClassName=label} }. A prompt is required (open-vocabulary). la_capi exposes a label per box (no class-id/score/mask), so Confidence is reported as 1.0 (greedy detection is deterministic).
• Static-links ggml so the .so only depends on libc/libstdc++/libgomp (bundled by the package step), like rfdetr-cpp.

Changes

• backend/go/locate-anything-cpp/ - the backend (main.go, golocateanythingcpp.go, CMakeLists.txt, Makefile, run.sh, package.sh, + Load/Detect wire test).
• .github/backend-matrix.yml - 9 build entries mirroring rfdetr-cpp (cuda-12/13, l4t-arm64, cpu, intel-sycl f16/f32, vulkan).
• backend/index.yaml + core/gallery/importers/locate-anything.go (+ test) - gallery entry + model importer (routes locate-anything GGUFs to this backend).
• Makefile - wired into test-extra.

Validation

Built locally (4 .so variants + the Go binary, CGO_ENABLED=0, go vet/gofmt clean). The Detect wire test passes end-to-end on the real model: gRPC LoadModel (q8_0 GGUF) -> Detect on a COCO street image with prompt person</c>car -> labeled boxes (TestDetect PASS, ~50s on CPU). Importer tests pass (go test ./core/gallery/importers/...).

Follow-ups

• bump_deps.yaml: the daily auto-bump registration for LOCATEANYTHING_VERSION is not in this PR - the pushing token lacked workflow scope. It should be added to .github/workflows/bump_deps.yaml:

  - repository: "mudler/locate-anything.cpp"
    variable: "LOCATEANYTHING_VERSION"
    branch: "master"
    file: "backend/go/locate-anything-cpp/Makefile"

• DCO: commits carry an Assisted-by: trailer per the AI-assistance policy; they need the human submitter's Signed-off-by to pass the DCO check.

AI-assisted (Claude Code, Opus 4.8); the human submitter owns, reviews, and is responsible for the change.