feat(server): add support for extra maps in adapter configuration

* Introduced ExtraMapConfig to allow multiple adapter configurations.
* Updated server and handler to utilize extra maps for routing.
* Added dashboard handler for metrics visualization.

pkg/server/handler.go

@@ -14,12 +14,28 @@ import (
 	"github.com/Warky-Devs/vecna.git/pkg/embedclient"
 )
 
+// ExtraMap pairs a dimension adapter with an optional forward-target override.
+type ExtraMap struct {
+	Adapter       adapter.Adapter
+	ForwardTarget string // named target in forward.targets; empty = model-based resolution
+}
+
 // handler holds shared dependencies for all HTTP handlers.
 type handler struct {
-	cfg     *config.Config
-	clients map[string]embedclient.Client
-	adapter adapter.Adapter
-	logger  *zap.Logger
+	cfg       *config.Config
+	clients   map[string]embedclient.Client
+	adapter   adapter.Adapter
+	extraMaps map[string]ExtraMap
+	logger    *zap.Logger
+}
+
+// resolveExtraMap returns the ExtraMap for the named extra_map entry.
+func (h *handler) resolveExtraMap(name string) (ExtraMap, error) {
+	em, ok := h.extraMaps[name]
+	if !ok {
+		return ExtraMap{}, fmt.Errorf("extra_map %q not configured", name)
+	}
+	return em, nil
 }
 
 // resolveClient selects the embed client for the given model name.
@@ -32,12 +48,24 @@ func (h *handler) resolveClient(model string) (embedclient.Client, string, strin
 	name := h.cfg.Forward.Default
 	c, ok := h.clients[name]
 	if !ok {
-		// No configured client — return a nil-safe error client
 		return &errClient{err: fmt.Errorf("no client configured for model %q and no default", model)}, name, ""
 	}
 	return c, name, firstEndpointURL(h.cfg, name)
 }
 
+// resolveClientOverride selects the client for targetOverride when set,
+// otherwise falls back to model-based resolution.
+func (h *handler) resolveClientOverride(targetOverride, model string) (embedclient.Client, string, string) {
+	if targetOverride == "" {
+		return h.resolveClient(model)
+	}
+	c, ok := h.clients[targetOverride]
+	if !ok {
+		return &errClient{err: fmt.Errorf("extra_map forward_target %q not configured", targetOverride)}, targetOverride, ""
+	}
+	return c, targetOverride, firstEndpointURL(h.cfg, targetOverride)
+}
+
 func firstEndpointURL(cfg *config.Config, targetName string) string {
 	t, ok := cfg.Forward.Targets[targetName]
 	if !ok || len(t.Endpoints) == 0 {