feat(config): add support for disabling OpenAI compatibility providers

- Introduced a `Disabled` flag to OpenAI compatibility configurations.
- Updated routing, auth selection, and API handling logic to respect the `Disabled` state.
- Extended relevant APIs, YAML configurations, and data structures to include the `Disabled` field.
- Adjusted all relevant loops and filters to skip disabled providers.

Closes: #3060 #3059 #2977

internal/watcher/clients.go

@@ -357,6 +357,9 @@ func BuildAPIKeyClients(cfg *config.Config) (int, int, int, int, int) {
 	}
 	if len(cfg.OpenAICompatibility) > 0 {
 		for _, compatConfig := range cfg.OpenAICompatibility {
+			if compatConfig.Disabled {
+				continue
+			}
 			openAICompatCount += len(compatConfig.APIKeyEntries)
 		}
 	}

internal/watcher/diff/openai_compat.go

@@ -66,6 +66,9 @@ func describeOpenAICompatibilityUpdate(oldEntry, newEntry config.OpenAICompatibi
 	oldModelCount := countOpenAIModels(oldEntry.Models)
 	newModelCount := countOpenAIModels(newEntry.Models)
 	details := make([]string, 0, 3)
+	if oldEntry.Disabled != newEntry.Disabled {
+		details = append(details, fmt.Sprintf("disabled %t -> %t", oldEntry.Disabled, newEntry.Disabled))
+	}
 	if oldKeyCount != newKeyCount {
 		details = append(details, fmt.Sprintf("api-keys %d -> %d", oldKeyCount, newKeyCount))
 	}

internal/watcher/synthesizer/config.go

@@ -194,6 +194,9 @@ func (s *ConfigSynthesizer) synthesizeOpenAICompat(ctx *SynthesisContext) []*cor
 	out := make([]*coreauth.Auth, 0)
 	for i := range cfg.OpenAICompatibility {
 		compat := &cfg.OpenAICompatibility[i]
+		if compat.Disabled {
+			continue
+		}
 		prefix := strings.TrimSpace(compat.Prefix)
 		providerName := strings.ToLower(strings.TrimSpace(compat.Name))
 		if providerName == "" {