fix(server): multi step tool call (#13486)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

- Bug Fixes
- Enforced a consistent step limit for AI responses across providers,
preventing excessively long generations in both text and streaming modes
for more predictable results.

- Refactor
- Centralized step limit configuration into a shared provider, ensuring
uniform behavior across providers and simplifying future maintenance.
- Standardized application of step limits in text generation and
streaming flows to align provider behavior and improve overall
reliability.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/backend/server/src/plugins/copilot/providers/anthropic/anthropic.ts

@@ -26,8 +26,6 @@ import {
 } from '../utils';
 
 export abstract class AnthropicProvider<T> extends CopilotProvider<T> {
-  private readonly MAX_STEPS = 20;
-
   protected abstract instance:
     | AnthropicSDKProvider
     | GoogleVertexAnthropicProvider;

packages/backend/server/src/plugins/copilot/providers/gemini/gemini.ts

@@ -9,6 +9,7 @@ import {
   generateObject,
   generateText,
   JSONParseError,
+  stepCountIs,
   streamText,
 } from 'ai';
 
@@ -85,6 +86,7 @@ export abstract class GeminiProvider<T> extends CopilotProvider<T> {
           google: this.getGeminiOptions(options, model.id),
         },
         tools: await this.getTools(options, model.id),
+        stopWhen: stepCountIs(this.MAX_STEPS),
       });
 
       if (!text) throw new Error('Failed to generate text');
@@ -276,6 +278,7 @@ export abstract class GeminiProvider<T> extends CopilotProvider<T> {
         google: this.getGeminiOptions(options, model.id),
       },
       tools: await this.getTools(options, model.id),
+      stopWhen: stepCountIs(this.MAX_STEPS),
     });
     return fullStream;
   }

packages/backend/server/src/plugins/copilot/providers/openai.ts

@@ -296,8 +296,6 @@ export class OpenAIProvider extends CopilotProvider<OpenAIConfig> {
     },
   ];
 
-  private readonly MAX_STEPS = 20;
-
   #instance!: VercelOpenAIProvider;
 
   override configured(): boolean {

packages/backend/server/src/plugins/copilot/providers/provider.ts

@@ -55,6 +55,7 @@ import {
 @Injectable()
 export abstract class CopilotProvider<C = any> {
   protected readonly logger = new Logger(this.constructor.name);
+  protected readonly MAX_STEPS = 20;
   protected onlineModelList: string[] = [];
   abstract readonly type: CopilotProviderType;
   abstract readonly models: CopilotProviderModel[];