feat(config): add support for model prefixes and prefix normalization

Refactor model management to include an optional `prefix` field for model credentials, enabling better namespace handling. Update affected configuration files, APIs, and handlers to support prefix normalization and routing. Remove unused OpenAI compatibility provider logic to simplify processing.

internal/config/config.go

@@ -187,6 +187,9 @@ type ClaudeKey struct {
 	// APIKey is the authentication key for accessing Claude API services.
 	APIKey string `yaml:"api-key" json:"api-key"`
 
+	// Prefix optionally namespaces models for this credential (e.g., "teamA/claude-sonnet-4").
+	Prefix string `yaml:"prefix,omitempty" json:"prefix,omitempty"`
+
 	// BaseURL is the base URL for the Claude API endpoint.
 	// If empty, the default Claude API URL will be used.
 	BaseURL string `yaml:"base-url" json:"base-url"`
@@ -219,6 +222,9 @@ type CodexKey struct {
 	// APIKey is the authentication key for accessing Codex API services.
 	APIKey string `yaml:"api-key" json:"api-key"`
 
+	// Prefix optionally namespaces models for this credential (e.g., "teamA/gpt-5-codex").
+	Prefix string `yaml:"prefix,omitempty" json:"prefix,omitempty"`
+
 	// BaseURL is the base URL for the Codex API endpoint.
 	// If empty, the default Codex API URL will be used.
 	BaseURL string `yaml:"base-url" json:"base-url"`
@@ -239,6 +245,9 @@ type GeminiKey struct {
 	// APIKey is the authentication key for accessing Gemini API services.
 	APIKey string `yaml:"api-key" json:"api-key"`
 
+	// Prefix optionally namespaces models for this credential (e.g., "teamA/gemini-3-pro-preview").
+	Prefix string `yaml:"prefix,omitempty" json:"prefix,omitempty"`
+
 	// BaseURL optionally overrides the Gemini API endpoint.
 	BaseURL string `yaml:"base-url,omitempty" json:"base-url,omitempty"`
 
@@ -258,6 +267,9 @@ type OpenAICompatibility struct {
 	// Name is the identifier for this OpenAI compatibility configuration.
 	Name string `yaml:"name" json:"name"`
 
+	// Prefix optionally namespaces model aliases for this provider (e.g., "teamA/kimi-k2").
+	Prefix string `yaml:"prefix,omitempty" json:"prefix,omitempty"`
+
 	// BaseURL is the base URL for the external OpenAI-compatible API endpoint.
 	BaseURL string `yaml:"base-url" json:"base-url"`
 
@@ -422,6 +434,7 @@ func (cfg *Config) SanitizeOpenAICompatibility() {
 	for i := range cfg.OpenAICompatibility {
 		e := cfg.OpenAICompatibility[i]
 		e.Name = strings.TrimSpace(e.Name)
+		e.Prefix = normalizeModelPrefix(e.Prefix)
 		e.BaseURL = strings.TrimSpace(e.BaseURL)
 		e.Headers = NormalizeHeaders(e.Headers)
 		if e.BaseURL == "" {
@@ -442,6 +455,7 @@ func (cfg *Config) SanitizeCodexKeys() {
 	out := make([]CodexKey, 0, len(cfg.CodexKey))
 	for i := range cfg.CodexKey {
 		e := cfg.CodexKey[i]
+		e.Prefix = normalizeModelPrefix(e.Prefix)
 		e.BaseURL = strings.TrimSpace(e.BaseURL)
 		e.Headers = NormalizeHeaders(e.Headers)
 		e.ExcludedModels = NormalizeExcludedModels(e.ExcludedModels)
@@ -460,6 +474,7 @@ func (cfg *Config) SanitizeClaudeKeys() {
 	}
 	for i := range cfg.ClaudeKey {
 		entry := &cfg.ClaudeKey[i]
+		entry.Prefix = normalizeModelPrefix(entry.Prefix)
 		entry.Headers = NormalizeHeaders(entry.Headers)
 		entry.ExcludedModels = NormalizeExcludedModels(entry.ExcludedModels)
 	}
@@ -479,6 +494,7 @@ func (cfg *Config) SanitizeGeminiKeys() {
 		if entry.APIKey == "" {
 			continue
 		}
+		entry.Prefix = normalizeModelPrefix(entry.Prefix)
 		entry.BaseURL = strings.TrimSpace(entry.BaseURL)
 		entry.ProxyURL = strings.TrimSpace(entry.ProxyURL)
 		entry.Headers = NormalizeHeaders(entry.Headers)
@@ -492,6 +508,18 @@ func (cfg *Config) SanitizeGeminiKeys() {
 	cfg.GeminiKey = out
 }
 
+func normalizeModelPrefix(prefix string) string {
+	trimmed := strings.TrimSpace(prefix)
+	trimmed = strings.Trim(trimmed, "/")
+	if trimmed == "" {
+		return ""
+	}
+	if strings.Contains(trimmed, "/") {
+		return ""
+	}
+	return trimmed
+}
+
 func syncInlineAccessProvider(cfg *Config) {
 	if cfg == nil {
 		return