pkg/miner: pluggable inference-engine backend interface (closes 3 TODOs)

[abhicris]

Problem

pkg/miner/miner.go has three // TODO: stubs that keep the miner from executing real inference work:

• pkg/miner/miner.go:326 — // TODO: Integrate with actual inference engine (llama.cpp, vllm, etc.) (inside runInference)
• pkg/miner/miner.go:356 — // TODO: Integrate with actual chat model (inside runChat)
• pkg/miner/miner.go:381 — // TODO: Integrate with embedding model (inside runEmbedding)

All three currently return hard-coded placeholder responses. The miner ships a working queue/API/result loop, but the compute layer is a stub.

Proposal

Introduce a small pluggable backend interface rather than hard-wiring any specific engine binary. That keeps luxfi/ai binary-light while letting operators point at whichever engine they run.

// pkg/miner/backend/backend.go
type InferenceBackend interface {
    Chat(ctx, ChatRequest) (ChatResponse, error)
    Inference(ctx, InferenceRequest) (InferenceResponse, error)
    Embed(ctx, EmbedRequest) (EmbedResponse, error)
    Capabilities() Capabilities
    Name() string
}

Ship two reference backends:

1. backend/noop — current deterministic placeholder extracted verbatim. Preserves today's behaviour so existing tests pass unchanged. Default.
2. backend/openai — OpenAI-compatible HTTP adapter (stdlib net/http, no new deps). Since llama.cpp / vllm / ollama all expose an OpenAI-compatible /v1/chat/completions, one adapter covers all three via OPENAI_API_BASE config.

Config extension: Config.Backend (noop | openai) plus Config.OpenAIBase / Config.OpenAIAPIKey / Config.OpenAIModel. Default stays noop — zero behaviour change for existing callers.

Scope

• pkg/miner/backend/backend.go — interface + request/response types
• pkg/miner/backend/noop/noop.go — deterministic mock
• pkg/miner/backend/openai/openai.go — HTTP adapter
• Wire Miner.processTask to dispatch through backend
• Unit tests for interface contract, noop, and openai (httptest-mocked server)
• pkg/miner/backend/README.md — short doc with llama.cpp / vllm / ollama pointer commands

Target: ~500–800 LOC, no new go.mod deps, default behaviour preserved.

Happy to send the PR directly.

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Contributed by kcolbchain (https://kcolbchain.com) · https://abhishekkrishna.com