feat: add configurable response format for AI agents (text/JSON) (#15953)

## Summary
This PR adds configurable response format support for AI agents,
allowing them to return either plain text or structured JSON data based
on a defined schema.

## Key Features

### 1. Agent Response Format Configuration
- Added `AgentResponseFormat` type supporting:
  - `text`: Returns plain text responses (default)
  - `json`: Returns structured JSON based on defined schema
- New `AgentResponseSchema` type moved to `twenty-shared/ai` for sharing
between frontend/backend

### 2. Settings UI
- New `SettingsAgentResponseFormat` component for configuring response
format
- Visual schema builder for defining JSON output structure
- Real-time validation and preview
- Integrated into agent settings tab

### 3. Workflow Integration
- AI Agent workflow action automatically uses agent's configured
response format
- Output schema dynamically generated from agent's response format
- Workflow variable picker shows structured fields for JSON responses
- Backward compatible with existing text-only agents

### 4. Backend Implementation
- Added `convertAgentSchemaToZod` utility to validate JSON responses
- Agent executor service handles both text and JSON generation
- Automatic agent creation/cloning when adding AI agent steps to
workflows
- Unique agent naming with conflict resolution

### 5. Database Migration
- Migration `1763622159656-update-agent-response-format.ts` 
- Sets default `responseFormat` to `{"type":"text"}` for existing agents
- Updated all standard agents with proper response format

## Changes by Module

### Frontend (`twenty-front`)
- 🆕 `AgentResponseFormat` type
- 🆕 `SettingsAgentResponseFormat` component
- ✏️ Updated `WorkflowEditActionAiAgent` to support response format
configuration
- 🗑️ Removed deprecated `useAiAgentOutputSchema` hook and
`AiAgentOutputSchema` type

### Backend (`twenty-server`)
- 🆕 `AgentResponseFormat` type in agent entity
- 🆕 `convertAgentSchemaToZod` utility for schema validation
- ✏️ Updated `AiAgentExecutorService` to handle both text and JSON
generation
- ✏️ Updated `WorkflowSchemaWorkspaceService` to generate output schema
from agent config
- ✏️ Enhanced `WorkflowVersionStepOperationsWorkspaceService` with agent
creation/cloning
- 🆕 Agent naming constants for conflict resolution

### Shared (`twenty-shared`)
- 🆕 `AgentResponseSchema` type
- 🆕 `ModelConfiguration` type moved to shared package
- Updated exports in `ai/index.ts`

## Code Quality
- Removed useless comments following code style guidelines
- All linter checks passed
- Type-safe implementation with proper TypeScript types

## Testing
- ✅ Database migration tested
- ✅ Agent creation/cloning in workflows verified
- ✅ Response format switching (text ↔ JSON) validated
- ✅ Backward compatibility with existing agents confirmed

## Migration Notes
- Existing agents will have `responseFormat: {type: 'text'}` set
automatically
- No breaking changes - all existing functionality preserved
- Agents can be updated to use JSON format through settings UI

packages/twenty-server/src/engine/metadata-modules/agent/agent.entity.ts

@@ -16,6 +16,7 @@ import { SyncableEntity } from 'src/engine/workspace-manager/workspace-sync/inte
 
 import { ModelId } from 'src/engine/core-modules/ai/constants/ai-models.const';
 import { WorkspaceEntity } from 'src/engine/core-modules/workspace/workspace.entity';
+import { AgentResponseFormat } from 'src/engine/metadata-modules/agent/types/agent-response-format.type';
 import { ModelConfiguration } from 'src/engine/metadata-modules/agent/types/modelConfiguration';
 
 import { AgentHandoffEntity } from './agent-handoff.entity';
@@ -54,8 +55,8 @@ export class AgentEntity
   @Column({ nullable: false, type: 'varchar', default: 'auto' })
   modelId: ModelId;
 
-  @Column({ nullable: true, type: 'jsonb' })
-  responseFormat: object;
+  @Column({ nullable: true, type: 'jsonb', default: { type: 'text' } })
+  responseFormat: AgentResponseFormat;
 
   @Column({ nullable: false, type: 'uuid' })
   workspaceId: string;