Derive provider from model ID

The provider is always the prefix before "/" in the model ID,
so storing it as a separate field is redundant. Replace the
field with a Provider() method.

Signed-off-by: Aurélien Sibiril <81782+aureliensibiril@users.noreply.github.com>

internal/cmd/genmodels/main.go

@@ -136,7 +136,6 @@ var generatedModels = map[string]ModelDefinition{
 			&buf,
 			`	%q: {
 		Name:            %q,
-		Provider:        %q,
 		ContextLength:   %d,
 		MaxOutputTokens: %d,
 		Supports: SupportedParameters{
@@ -145,7 +144,6 @@ var generatedModels = map[string]ModelDefinition{
 `,
 			m.ID,
 			m.Name,
-			provider,
 			m.ContextLen,
 			m.TopProvider.MaxCompletionTokens,
 			buildSupports(m.SupportedParams),