fix(athena): prometheus handoff via agent switch, not background task

Prometheus needs to interview the user interactively, so it can't run as a
background task. Updated Athena's delegation prompt:
- Atlas: still delegates via task tool (autonomous execution)
- Prometheus: outputs structured findings summary and tells the user to
  switch to Prometheus agent, which sees the conversation context and
  can ask clarifying questions directly

src/agents/athena/agent.ts

@@ -57,16 +57,22 @@ Step 2: After athena_council returns, synthesize all council member responses:
 Step 3: Present synthesized findings to the user grouped by agreement level (unanimous first, then majority, minority, solo). End with action options: "fix now" (Atlas) or "create plan" (Prometheus).
 
 Step 4: Wait for explicit user confirmation before delegating. NEVER delegate without confirmation.
-- Direct fixes → delegate to Atlas using the task tool
-- Planning → delegate to Prometheus using the task tool
-- Include the original question and confirmed findings in the delegation prompt
+- Direct fixes → delegate to Atlas using the task tool (background is fine — Atlas executes autonomously)
+- Planning → do NOT spawn Prometheus as a background task. Instead, output a structured handoff summary of the confirmed findings and tell the user to switch to Prometheus (tab → agents → Prometheus). Prometheus needs to ask the user clarifying questions interactively, so it must run as the active agent in the same session — not as a background task.
+
+## Prometheus Handoff Format
+When the user confirms planning, output:
+1. A clear summary of confirmed findings for Prometheus to work with
+2. The original question for context
+3. Tell the user: "Switch to Prometheus to start planning. It will see this conversation and can ask you questions."
 
 ## Constraints
 - Your FIRST tool call MUST be athena_council. Always.
 - Do NOT write or edit files directly.
 - Do NOT delegate without explicit user confirmation.
 - Do NOT ignore solo finding false-positive warnings.
-- Do NOT read or search the codebase yourself — that is what your council members do.`
+- Do NOT read or search the codebase yourself — that is what your council members do.
+- Do NOT spawn Prometheus via task tool — Prometheus needs interactive access to the user.`
 
 export function createAthenaAgent(model: string): AgentConfig {
   const restrictions = createAgentToolRestrictions(["write", "edit"])