fix: stamp MCP and AI Agent writes with FieldActorSource.AGENT (#22215)

## Description
Fixes #21437 MCP and AI Agent writes now correctly stamped with

### Problem
Records created through MCP server were stamped as `WORKFLOW`, making
them indistinguishable from workflow-created records. This breaks
loop-protection filters that skip workflow-originated records.

### Solution
- MCP writes now correctly stamped with `createdBy.source = AGENT`
- AI Agent execution now uses `AGENT` instead of `MANUAL`
- Added `WorkspaceCacheModule` to MCP module
- Updated tests to verify AGENT source

### Files Changed
- `mcp.module.ts`: Added WorkspaceCacheModule import
- `mcp-protocol.service.ts`: Set AGENT source in buildMcpToolSet
- `mcp-protocol.service.spec.ts`: Updated tests
- `agent-actor-context.service.ts`: Changed MANUAL → AGENT
- 

## Type of Change
- [x] Bug fix (non-breaking change)

## Checklist
- [x] Code follows project style
- [x] Tests added/updated
- [x] Issue linked

Fixes #21437

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packages/twenty-server/src/engine/metadata-modules/ai/ai-agent-execution/services/agent-actor-context.service.ts

@@ -1,6 +1,6 @@
 import { Injectable } from '@nestjs/common';
 
-import { type ActorMetadata } from 'twenty-shared/types';
+import { type ActorMetadata, FieldActorSource } from 'twenty-shared/types';
 
 import { buildCreatedByFromFullNameMetadata } from 'src/engine/core-modules/actor/utils/build-created-by-from-full-name-metadata.util';
 import { UserWorkspaceService } from 'src/engine/core-modules/user-workspace/user-workspace.service';
@@ -90,10 +90,13 @@ export class AgentActorContextService {
       );
     }
 
-    const actorContext = buildCreatedByFromFullNameMetadata({
-      fullNameMetadata: workspaceMember.name,
-      workspaceMemberId: workspaceMember.id,
-    });
+    const actorContext: ActorMetadata = {
+      ...buildCreatedByFromFullNameMetadata({
+        fullNameMetadata: workspaceMember.name,
+        workspaceMemberId: workspaceMember.id,
+      }),
+      source: FieldActorSource.AGENT,
+    };
 
     const userContext: UserContext = {
       firstName: workspaceMember.name?.firstName ?? '',