refactor provider interface to return models with metadata

- replaced old TranscriptionModels/LLMModels/SupportsX methods with Models() []Model
- added DefaultModel(t ModelType), IsLocal() to interface
- added helpers: GetModel, ModelsOfType, FindModelByID, ModelsForLanguage, ValidateModelLanguage
- all providers now return full Model metadata with SupportedLanguages, AdapterType, Endpoint
- groq distil-whisper-large-v3-en marked as english-only
- updated TUI to use new interface

internal/provider/provider.go

@@ -1,16 +1,19 @@
 package provider
 
+import (
+	"errors"
+	"fmt"
+	"strings"
+)
+
 // Provider defines the interface for a transcription/LLM service provider
 type Provider interface {
 	Name() string
 	RequiresAPIKey() bool
 	ValidateAPIKey(key string) bool
-	SupportsTranscription() bool
-	SupportsLLM() bool
-	DefaultTranscriptionModel() string
-	DefaultLLMModel() string
-	TranscriptionModels() []string
-	LLMModels() []string
+	IsLocal() bool
+	Models() []Model
+	DefaultModel(t ModelType) string
 }
 
 // ProviderConfig holds configuration for a single provider
@@ -50,7 +53,7 @@ func ListProviders() []string {
 func ListProvidersWithTranscription() []string {
 	var names []string
 	for name, p := range registry {
-		if p.SupportsTranscription() {
+		if hasModelsOfType(p, Transcription) {
 			names = append(names, name)
 		}
 	}
@@ -61,9 +64,104 @@ func ListProvidersWithTranscription() []string {
 func ListProvidersWithLLM() []string {
 	var names []string
 	for name, p := range registry {
-		if p.SupportsLLM() {
+		if hasModelsOfType(p, LLM) {
 			names = append(names, name)
 		}
 	}
 	return names
 }
+
+// hasModelsOfType returns true if provider has any models of the given type
+func hasModelsOfType(p Provider, t ModelType) bool {
+	for _, m := range p.Models() {
+		if m.Type == t {
+			return true
+		}
+	}
+	return false
+}
+
+// GetModel returns a model from a specific provider, or error if not found
+func GetModel(providerName, modelID string) (*Model, error) {
+	p := GetProvider(providerName)
+	if p == nil {
+		return nil, fmt.Errorf("unknown provider: %s", providerName)
+	}
+
+	for _, m := range p.Models() {
+		if m.ID == modelID {
+			return &m, nil
+		}
+	}
+	return nil, fmt.Errorf("model %s not found in provider %s", modelID, providerName)
+}
+
+// ModelsOfType returns all models of the given type from a provider
+func ModelsOfType(p Provider, t ModelType) []Model {
+	var result []Model
+	for _, m := range p.Models() {
+		if m.Type == t {
+			result = append(result, m)
+		}
+	}
+	return result
+}
+
+// FindModelByID searches all providers for a model with the given ID
+func FindModelByID(modelID string) (*Model, Provider, error) {
+	for _, p := range registry {
+		for _, m := range p.Models() {
+			if m.ID == modelID {
+				return &m, p, nil
+			}
+		}
+	}
+	return nil, nil, fmt.Errorf("model %s not found in any provider", modelID)
+}
+
+// ModelsForLanguage returns models from a provider that support the given language
+func ModelsForLanguage(p Provider, t ModelType, langCode string) []Model {
+	var result []Model
+	for _, m := range p.Models() {
+		if m.Type == t && m.SupportsLanguage(langCode) {
+			result = append(result, m)
+		}
+	}
+	return result
+}
+
+// ValidateModelLanguage checks if a model supports the given language.
+// Returns error with list of supported languages if not supported.
+// Returns nil if langCode is "" (auto) - auto is always supported.
+func ValidateModelLanguage(providerName, modelID, langCode string) error {
+	if langCode == "" {
+		return nil // auto always supported
+	}
+
+	model, err := GetModel(providerName, modelID)
+	if err != nil {
+		return err
+	}
+
+	if model.SupportsLanguage(langCode) {
+		return nil
+	}
+
+	// truncate supported languages list for error message
+	supported := model.SupportedLanguages
+	if len(supported) > 10 {
+		supported = append(supported[:10], "...")
+	}
+
+	return fmt.Errorf(
+		"model %s does not support language '%s'. Supported: %s",
+		modelID,
+		langCode,
+		strings.Join(supported, ", "),
+	)
+}
+
+var (
+	ErrProviderNotFound = errors.New("provider not found")
+	ErrModelNotFound    = errors.New("model not found")
+)