fix(agents): add anti-duplication rules to Prometheus and Metis agents

- Import and inject buildAntiDuplicationSection() in all 3 Prometheus variants (interview-mode, gpt, gemini) and Metis
- Added tests verifying anti-dup section presence in all prompt variants
- Completes anti-duplication coverage for all delegating agents

src/agents/metis.ts

@@ -1,5 +1,6 @@
 import type { AgentConfig } from "@opencode-ai/sdk"
 import type { AgentMode, AgentPromptMetadata } from "./types"
+import { buildAntiDuplicationSection } from "../dynamic-agent-prompt-builder"
 import { createAgentToolRestrictions } from "../shared/permission-compat"
 
 const MODE: AgentMode = "subagent"
@@ -25,6 +26,8 @@ export const METIS_SYSTEM_PROMPT = `# Metis - Pre-Planning Consultant
 - **READ-ONLY**: You analyze, question, advise. You do NOT implement or modify files.
 - **OUTPUT**: Your analysis feeds into Prometheus (planner). Be actionable.
 
+${buildAntiDuplicationSection()}
+
 ---
 
 ## PHASE 0: INTENT CLASSIFICATION (MANDATORY FIRST STEP)