ui : add the Enable Discover Models setting

The flag gates browsing and downloading HuggingFace GGUF models, so it is
declared on the discover layer; the repo-tree lookup in the manager layer
above reads it from here.

Assisted-by: pi:llama.cpp/DeepSeek-V4.1-Flash

tools/ui/src/lib/constants/settings-keys.constants.ts

@@ -26,6 +26,7 @@ export const SETTINGS_KEYS = {
 	DYNATEMP_EXPONENT: 'dynatemp_exponent',
 	DYNATEMP_RANGE: 'dynatemp_range',
 	ENABLE_CONTINUE_GENERATION: 'enableContinueGeneration',
+	ENABLE_DISCOVER_MODELS: 'enableDiscoverModels',
 	EXCLUDE_REASONING_FROM_CONTEXT: 'excludeReasoningFromContext',
 	FREQUENCY_PENALTY: 'frequency_penalty',
 	FULL_HEIGHT_CODE_BLOCKS: 'fullHeightCodeBlocks',

tools/ui/src/lib/constants/settings.constants.ts

@@ -128,6 +128,13 @@ export const SETTINGS_REGISTRY: SettingsSectionEntry[] = [
 				label: 'Enable "Continue" button',
 				type: SettingsFieldType.CHECKBOX
 			},
+			{
+				defaultValue: true,
+				help: 'Show the Discover Models sidebar action to browse and download HuggingFace GGUF models. Only available in router mode.',
+				key: SETTINGS_KEYS.ENABLE_DISCOVER_MODELS,
+				label: 'Enable Discover Models',
+				type: SettingsFieldType.CHECKBOX
+			},
 			{
 				defaultValue: true,
 				help: 'Fetch model metadata (avatars, context length, chat template, file sizes) from the Hugging Face Hub. When off, the UI only shows what the server reports for /v1/models and hides the org avatars.',