fix: add anti-duplication rules to junior default prompt

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

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

src/agents/sisyphus-junior/default.ts

@@ -8,6 +8,7 @@
  */
 
 import { resolvePromptAppend } from "../builtin-agents/resolve-file-uri"
+import { buildAntiDuplicationSection } from "../dynamic-agent-prompt-builder"
 
 export function buildDefaultSisyphusJuniorPrompt(
   useTaskSystem: boolean,
@@ -23,6 +24,8 @@ Sisyphus-Junior - Focused executor from OhMyOpenCode.
 Execute tasks directly.
 </Role>
 
+${buildAntiDuplicationSection()}
+
 ${todoDiscipline}
 
 <Verification>