feat(usage): add support for requested model alias handling

- Introduced methods for setting and retrieving model aliases in execution and usage contexts.
- Enhanced `UsageReporter` and related structures to include client-requested aliases.
- Updated tests to validate alias propagation and ensure correct usage reporting.
- Adjusted metadata handling in CLIProxyAPI executors to address alias integration.

sdk/cliproxy/usage/manager.go

@@ -2,6 +2,7 @@ package usage
 
 import (
 	"context"
+	"strings"
 	"sync"
 	"time"
 
@@ -12,6 +13,7 @@ import (
 type Record struct {
 	Provider    string
 	Model       string
+	Alias       string
 	APIKey      string
 	AuthID      string
 	AuthIndex   string
@@ -32,6 +34,36 @@ type Detail struct {
 	TotalTokens     int64
 }
 
+type requestedModelAliasContextKey struct{}
+
+// WithRequestedModelAlias stores the client-requested model name for usage sinks.
+func WithRequestedModelAlias(ctx context.Context, alias string) context.Context {
+	if ctx == nil {
+		ctx = context.Background()
+	}
+	alias = strings.TrimSpace(alias)
+	if alias == "" {
+		return ctx
+	}
+	return context.WithValue(ctx, requestedModelAliasContextKey{}, alias)
+}
+
+// RequestedModelAliasFromContext returns the client-requested model name stored in ctx.
+func RequestedModelAliasFromContext(ctx context.Context) string {
+	if ctx == nil {
+		return ""
+	}
+	raw := ctx.Value(requestedModelAliasContextKey{})
+	switch value := raw.(type) {
+	case string:
+		return strings.TrimSpace(value)
+	case []byte:
+		return strings.TrimSpace(string(value))
+	default:
+		return ""
+	}
+}
+
 // Plugin consumes usage records emitted by the proxy runtime.
 type Plugin interface {
 	HandleUsage(ctx context.Context, record Record)