refactor(llm): deduplicate and validate auth header normalization

Export NormalizeAuthHeader from the llm package and remove the duplicate
normalizeConfigAuthHeader in config_cmd.go. Invalid auth_header values
now return an error at configuration time instead of being silently
accepted and causing opaque 401s at runtime.

cmd/opencodereview/config_cmd.go

@@ -6,7 +6,8 @@ import (
 	"os"
 	"path/filepath"
 	"strconv"
-	"strings"
+
+	"github.com/open-code-review/open-code-review/internal/llm"
 )
 
 // Default config file location: ~/.opencodereview/config.json
@@ -132,7 +133,11 @@ func setConfigValue(cfg *Config, key, value string) error {
 	case "llm.auth_token", "llm.AuthToken":
 		cfg.Llm.AuthToken = value
 	case "llm.auth_header", "llm.AuthHeader":
-		cfg.Llm.AuthHeader = normalizeConfigAuthHeader(value)
+		normalized, err := llm.NormalizeAuthHeader(value)
+		if err != nil {
+			return err
+		}
+		cfg.Llm.AuthHeader = normalized
 	case "llm.model", "llm.Model":
 		cfg.Llm.Model = value
 	case "llm.use_anthropic", "llm.UseAnthropic":
@@ -175,18 +180,6 @@ func setConfigValue(cfg *Config, key, value string) error {
 	return nil
 }
 
-func normalizeConfigAuthHeader(header string) string {
-	header = strings.TrimSpace(header)
-	switch strings.ToLower(header) {
-	case "x-api-key":
-		return "x-api-key"
-	case "authorization", "bearer":
-		return "authorization"
-	default:
-		return header
-	}
-}
-
 func (c *Config) ensureTelemetry() {
 	if c.Telemetry == nil {
 		c.Telemetry = &TelemetryConfig{}

internal/llm/client.go

@@ -182,7 +182,7 @@ type ClientConfig struct {
 	URL        string         // Full API endpoint URL
 	APIKey     string         // Bearer token / API key
 	Model      string         // Default model override
-	AuthHeader string         // Anthropic auth header: "x-api-key" or "authorization"
+	AuthHeader string         // Auth header name: "x-api-key", "authorization", or empty for protocol default
 	Timeout    time.Duration  // Request timeout
 	ExtraBody  map[string]any // Vendor-specific fields merged into every request body
 }
@@ -484,7 +484,7 @@ func NewAnthropicClient(cfg ClientConfig) *AnthropicClient {
 	}
 
 	sdkBaseURL := strings.TrimSuffix(strings.TrimRight(cfg.URL, "/"), "/v1/messages")
-	authHeader := normalizeAuthHeader(cfg.AuthHeader)
+	authHeader, _ := NormalizeAuthHeader(cfg.AuthHeader)
 	if authHeader == "" {
 		authHeader = "authorization"
 	}

internal/llm/resolver.go

@@ -87,7 +87,11 @@ func tryOCREnv() (ResolvedEndpoint, bool, error) {
 
 	var authHeader string
 	if protocol == "anthropic" {
-		authHeader = normalizeAuthHeader(os.Getenv(envOCRLLMAuthHeader))
+		var err error
+		authHeader, err = NormalizeAuthHeader(os.Getenv(envOCRLLMAuthHeader))
+		if err != nil {
+			return ResolvedEndpoint{}, false, fmt.Errorf("OCR environment: %w", err)
+		}
 		if authHeader == "" {
 			authHeader = defaultAuthHeader(protocol)
 		}
@@ -141,7 +145,11 @@ func tryOCRConfig(path string) (ResolvedEndpoint, bool, error) {
 
 	var authHeader string
 	if protocol == "anthropic" {
-		authHeader = normalizeAuthHeader(cfg.Llm.AuthHeader)
+		var err error
+		authHeader, err = NormalizeAuthHeader(cfg.Llm.AuthHeader)
+		if err != nil {
+			return ResolvedEndpoint{}, false, fmt.Errorf("OCR config file: %w", err)
+		}
 		if authHeader == "" {
 			authHeader = defaultAuthHeader(protocol)
 		}
@@ -256,15 +264,20 @@ func defaultAuthHeader(protocol string) string {
 	return ""
 }
 
-func normalizeAuthHeader(header string) string {
+// NormalizeAuthHeader normalizes an auth header value to a canonical form.
+// It returns an error for unrecognized values.
+func NormalizeAuthHeader(header string) (string, error) {
 	header = strings.TrimSpace(header)
+	if header == "" {
+		return "", nil
+	}
 	switch strings.ToLower(header) {
 	case "x-api-key":
-		return "x-api-key"
+		return "x-api-key", nil
 	case "authorization", "bearer":
-		return "authorization"
+		return "authorization", nil
 	default:
-		return header
+		return "", fmt.Errorf("unsupported auth_header value %q; expected \"x-api-key\" or \"authorization\"", header)
 	}
 }