fix(ralph): harden execution boundaries

packages/workflow/workflow-workerthread/tests/source-worker.compat.spec.ts

@@ -8,6 +8,7 @@ import { expect, it, vi } from 'vitest'
 import { Context } from 'cordis'
 import type { Agent } from '@deepseek-ai/dsh-agent'
 import SubagentService from '@deepseek-ai/dsh-subagent'
+import type { SubagentProvider } from '@deepseek-ai/dsh-subagent'
 import WorkerWorkflowEngine from '../src/index.ts'
 import { SessionId } from '@deepseek-ai/dsh-session'
 
@@ -18,6 +19,13 @@ vi.setConfig({ testTimeout: 30_000 })
 it('runs the default config through the source worker', async () => {
   const ctx = new Context()
   const subagents = await ctx.plugin(SubagentService)
+  const provider: SubagentProvider = {
+    name: 'spawn',
+    capabilities: { outputSchema: true, depthLimit: true, toolFilter: true, persona: true },
+    inheritsParentContext: false,
+    start: () => Promise.reject(new Error('source-worker compat script must not start a child')),
+  }
+  ctx.subagents.registerProvider(provider)
   const engine = await ctx.plugin(WorkerWorkflowEngine, {})
   const parent = { id: SessionId('workflow-compat-parent'), options: {} } as unknown as Agent
   try {