Add output schema registry and public contract docs

internal/core/config/config.go

@@ -15,6 +15,7 @@ const (
 
 const (
 	DefaultModulesCSV                                     = "glossary,homophones,glossary,spoken_word,grammar"
+	DefaultOutputSchema                                   = "bare-segments"
 	DefaultPrimaryModel                                   = "openrouter/google/gemma-4-31b-it"
 	DefaultPrimaryBaseURL                                 = "https://openrouter.ai/api/v1"
 	DefaultPrimaryLLMTimeoutSeconds                       = 600
@@ -35,6 +36,7 @@ const (
 
 type Config struct {
 	Modules                   []string
+	OutputSchema              string
 	PrimaryLLM                LLMConfig
 	ValidationLLM             ValidationLLMConfig
 	TotalLLMConcurrency       int
@@ -91,7 +93,8 @@ func Default() Config {
 	modules, _ := ParseModulesCSV(DefaultModulesCSV)
 
 	return Config{
-		Modules: modules,
+		Modules:      modules,
+		OutputSchema: DefaultOutputSchema,
 		PrimaryLLM: LLMConfig{
 			Model:          DefaultPrimaryModel,
 			BaseURL:        DefaultPrimaryBaseURL,