feat: ModelRouter — unified OpenAI-compatible multi-source LLM gateway

- Lua adapters per upstream (transform_request/response/stream_chunk, build_headers signing hooks)
- AUTO priority routing with per-model kind (chat/image), explicit source/model routing
- Per-source concurrency caps with queueing, exponential backoff, AUTO failover
- OpenAI-compatible API: chat completions, SSE streaming, image generations, models
- Gateway key auth, web UI for adapter/source management, runtime persistence
- e2e test running the real binary against mocked upstreams

cmd/llmsproxy/main.go

@@ -0,0 +1,54 @@
+// Command llmsproxy is a standalone gateway that exposes multiple upstream LLM
+// sources behind a unified OpenAI-compatible HTTP API. Protocol differences are
+// handled by Lua adapters (per source), optionally signing outgoing requests.
+// It supports explicit model selection or AUTO routing by priority, image
+// generation, multimodal payloads, a web UI for adapter/source management, and
+// concurrent/queued scheduling with backoff and failover.
+package main
+
+import (
+	"flag"
+	"log"
+	"net/http"
+	"os"
+	"os/signal"
+	"syscall"
+	"time"
+
+	"llmsproxy/internal/core"
+	"llmsproxy/internal/gateway"
+)
+
+func main() {
+	cfgPath := flag.String("config", "config.yaml", "path to gateway config file")
+	flag.Parse()
+
+	c, err := core.New(*cfgPath)
+	if err != nil {
+		log.Fatalf("[llmsproxy] core: %v", err)
+	}
+	defer c.Close()
+
+	gw, err := gateway.New(c, c.GatewayKeys())
+	if err != nil {
+		log.Fatalf("[llmsproxy] gateway: %v", err)
+	}
+
+	srv := &http.Server{
+		Addr:              c.Listen(),
+		Handler:           gw.Handler(),
+		ReadHeaderTimeout: 10 * time.Second,
+	}
+	go func() {
+		log.Printf("[llmsproxy] listening on %s (default_model=%s, models=%v, adapters=%d)",
+			c.Listen(), c.DefaultModel(), c.Registry().ModelList(), len(c.ListAdapters()))
+		if err := srv.ListenAndServe(); err != nil && err != http.ErrServerClosed {
+			log.Fatalf("[llmsproxy] server: %v", err)
+		}
+	}()
+
+	stop := make(chan os.Signal, 1)
+	signal.Notify(stop, syscall.SIGINT, syscall.SIGTERM)
+	<-stop
+	log.Printf("[llmsproxy] shutting down")
+}