refactor: rename sisyphus_task to delegate_task

- Rename directories: sisyphus-task → delegate-task
- Rename types: SisyphusTaskArgs → DelegateTaskArgs, etc.
- Rename functions: createSisyphusTask → createDelegateTask
- Rename constants: SISYPHUS_TASK_* → DELEGATE_TASK_*
- Update tool name: sisyphus_task → delegate_task
- Update all prompts, docs, and tests

src/hooks/index.ts

@@ -30,4 +30,4 @@ export { createPrometheusMdOnlyHook } from "./prometheus-md-only";
 export { createTaskResumeInfoHook } from "./task-resume-info";
 export { createStartWorkHook } from "./start-work";
 export { createSisyphusOrchestratorHook } from "./sisyphus-orchestrator";
-export { createSisyphusTaskRetryHook } from "./sisyphus-task-retry";
+export { createDelegateTaskRetryHook } from "./delegate-task-retry";