feat: TextModel implementation wrapping llama-server

rocmModel implements inference.TextModel with Generate() and Chat()
methods that delegate to the llamacpp HTTP client, mapping go-inference
types to llama-server's OpenAI-compatible API. Token streaming via
iter.Seq[inference.Token] with mutex-protected error propagation.

Co-Authored-By: Virgil <virgil@lethean.io>
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

model.go

@@ -0,0 +1,102 @@
+//go:build linux && amd64
+
+package rocm
+
+import (
+	"context"
+	"iter"
+	"sync"
+
+	"forge.lthn.ai/core/go-inference"
+	"forge.lthn.ai/core/go-rocm/internal/llamacpp"
+)
+
+// rocmModel implements inference.TextModel using a llama-server subprocess.
+type rocmModel struct {
+	srv       *server
+	modelType string
+
+	mu      sync.Mutex
+	lastErr error
+}
+
+// Generate streams tokens for the given prompt via llama-server's /v1/completions endpoint.
+func (m *rocmModel) Generate(ctx context.Context, prompt string, opts ...inference.GenerateOption) iter.Seq[inference.Token] {
+	cfg := inference.ApplyGenerateOpts(opts)
+
+	req := llamacpp.CompletionRequest{
+		Prompt:        prompt,
+		MaxTokens:     cfg.MaxTokens,
+		Temperature:   cfg.Temperature,
+		TopK:          cfg.TopK,
+		TopP:          cfg.TopP,
+		RepeatPenalty: cfg.RepeatPenalty,
+	}
+
+	chunks, errFn := m.srv.client.Complete(ctx, req)
+
+	return func(yield func(inference.Token) bool) {
+		for text := range chunks {
+			if !yield(inference.Token{Text: text}) {
+				break
+			}
+		}
+		if err := errFn(); err != nil {
+			m.mu.Lock()
+			m.lastErr = err
+			m.mu.Unlock()
+		}
+	}
+}
+
+// Chat streams tokens from a multi-turn conversation via llama-server's /v1/chat/completions endpoint.
+func (m *rocmModel) Chat(ctx context.Context, messages []inference.Message, opts ...inference.GenerateOption) iter.Seq[inference.Token] {
+	cfg := inference.ApplyGenerateOpts(opts)
+
+	chatMsgs := make([]llamacpp.ChatMessage, len(messages))
+	for i, msg := range messages {
+		chatMsgs[i] = llamacpp.ChatMessage{
+			Role:    msg.Role,
+			Content: msg.Content,
+		}
+	}
+
+	req := llamacpp.ChatRequest{
+		Messages:      chatMsgs,
+		MaxTokens:     cfg.MaxTokens,
+		Temperature:   cfg.Temperature,
+		TopK:          cfg.TopK,
+		TopP:          cfg.TopP,
+		RepeatPenalty: cfg.RepeatPenalty,
+	}
+
+	chunks, errFn := m.srv.client.ChatComplete(ctx, req)
+
+	return func(yield func(inference.Token) bool) {
+		for text := range chunks {
+			if !yield(inference.Token{Text: text}) {
+				break
+			}
+		}
+		if err := errFn(); err != nil {
+			m.mu.Lock()
+			m.lastErr = err
+			m.mu.Unlock()
+		}
+	}
+}
+
+// ModelType returns the architecture identifier (e.g. "gemma3", "qwen3", "llama3").
+func (m *rocmModel) ModelType() string { return m.modelType }
+
+// Err returns the error from the last Generate/Chat call, if any.
+func (m *rocmModel) Err() error {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	return m.lastErr
+}
+
+// Close releases the llama-server subprocess and all associated resources.
+func (m *rocmModel) Close() error {
+	return m.srv.stop()
+}