fix(task): append plan delegation prompt requirements

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-opencode)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/tools/delegate-task/prompt-builder.ts

@@ -3,6 +3,14 @@ import { buildPlanAgentSystemPrepend, isPlanAgent } from "./constants"
 import { buildSystemContentWithTokenLimit } from "./token-limiter"
 
 const FREE_OR_LOCAL_PROMPT_TOKEN_LIMIT = 24000
+const PLAN_AGENT_PROMPT_APPEND = `
+
+Additional requirements for this planning request:
+- Answer in English.
+- Write the plan in English.
+- Plan well for ultrawork execution.
+- Use TDD-oriented planning.
+- Include a clear atomic commit strategy.`
 
 function usesFreeOrLocalModel(model: { providerID: string; modelID: string; variant?: string } | undefined): boolean {
   if (!model) {
@@ -52,3 +60,11 @@ export function buildSystemContent(input: BuildSystemContentInput): string | und
     effectiveMaxPromptTokens
   )
 }
+
+export function buildTaskPrompt(prompt: string, agentName: string | undefined): string {
+  if (!isPlanAgent(agentName)) {
+    return prompt
+  }
+
+  return `${prompt}${PLAN_AGENT_PROMPT_APPEND}`
+}