feat(ai/providers): dropped auto tool choice for reasoning models

- Add `shouldDropAutoToolChoiceForReasoning` helper to handle compatibility constraints for models where tool choice disables reasoning.
- Update OpenAI completions and responses parameter building to drop automatic tool choices when reasoning options are active.

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

@@ -108,7 +108,7 @@ export {
 
 import { ModelsConfigFile, type ProviderValidationModel, validateProviderConfiguration } from "./models-config";
 import type { ModelOverride, ModelsConfig, ProviderAuthMode } from "./models-config-schema";
-import { settings, type Settings } from "./settings";
+import { type Settings, settings } from "./settings";
 
 // DeviceCheck attestation (`x-oai-attestation`) for ChatGPT-OAuth Codex
 // requests; the pi-ai provider resolves it just-in-time per request.

packages/coding-agent/src/sdk.ts

@@ -1251,9 +1251,13 @@ async function createAgentSessionScoped(options: CreateAgentSessionOptions): Pro
 	// / session would silently miss credential_disabled events.
 	const modelRegistry =
 		options.modelRegistry ??
-		new ModelRegistry(options.authStorage ?? (await logger.time("discoverModels", discoverAuthStorage, agentDir)), undefined, {
-			settings,
-		});
+		new ModelRegistry(
+			options.authStorage ?? (await logger.time("discoverModels", discoverAuthStorage, agentDir)),
+			undefined,
+			{
+				settings,
+			},
+		);
 	// Track whether we internally created the authStorage so we can close it
 	// if construction fails before the session takes ownership.
 	const ownsAuthStorage = !options.authStorage && !options.modelRegistry;