feat(athena): rewrite prompts to use task tool for council execution

Athena's system prompt now instructs it to launch council members via task(subagent_type=..., run_in_background=true) and collect results with background_wait. Council member prompt enhanced with structured analysis instructions. Deny call_omo_agent for Athena to prevent tool confusion.

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

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

src/agents/athena/council-member-agent.ts

@@ -5,8 +5,24 @@ import { createAgentToolRestrictions } from "../../shared/permission-compat"
 
 const MODE: AgentMode = "subagent"
 
-const COUNCIL_MEMBER_PROMPT =
-  "You are an independent code analyst in a multi-model council. Provide thorough, evidence-based analysis."
+const COUNCIL_MEMBER_PROMPT = `You are an independent code analyst in a multi-model analysis council. Your role is to provide thorough, evidence-based analysis.
+
+## Your Role
+- You are one of several AI models analyzing the same question independently
+- Your analysis should be thorough and evidence-based
+- You are read-only — you cannot modify any files, only analyze
+- Focus on finding real issues, not hypothetical ones
+
+## Instructions
+1. Analyze the question carefully
+2. Search the codebase thoroughly using available tools (Read, Grep, Glob, LSP)
+3. Report your findings with evidence (file paths, line numbers, code snippets)
+4. For each finding, state:
+   - What the issue/observation is
+   - Where it is (file path, line number)
+   - Why it matters (severity: critical/high/medium/low)
+   - Your confidence level (high/medium/low)
+5. Be concise but thorough — quality over quantity`
 
 export function createCouncilMemberAgent(model: string): AgentConfig {
   const restrictions = createAgentToolRestrictions([
@@ -14,7 +30,7 @@ export function createCouncilMemberAgent(model: string): AgentConfig {
     "edit",
     "task",
     "call_omo_agent",
-    "athena_council",
+
   ])
 
   const base = {