fix(coding-agent): honor registered model base urls

closes #4063

packages/coding-agent/src/core/extensions/types.ts

@@ -1355,6 +1355,8 @@ export interface ProviderModelConfig {
 	name: string;
 	/** API type override for this model. */
 	api?: Api;
+	/** API endpoint URL override for this model. */
+	baseUrl?: string;
 	/** Whether the model supports extended thinking. */
 	reasoning: boolean;
 	/** Supported input types. */

packages/coding-agent/src/core/model-registry.ts

@@ -876,7 +876,7 @@ export class ModelRegistry {
 					name: modelDef.name,
 					api: api as Api,
 					provider: providerName,
-					baseUrl: config.baseUrl!,
+					baseUrl: modelDef.baseUrl ?? config.baseUrl!,
 					reasoning: modelDef.reasoning,
 					input: modelDef.input as ("text" | "image")[],
 					cost: modelDef.cost,