fix: add isPlanFamily for prometheus↔plan mutual blocking and task permission

- PLAN_AGENT_NAMES = ['plan'] (system prompt only)
- PLAN_FAMILY_NAMES = ['plan', 'prometheus'] (blocking + task permission)
- prometheus↔plan mutual delegation blocked via isPlanFamily()
- prometheus gets task tool permission via isPlanFamily()
- prompt-builder unchanged: prometheus does NOT get plan system prompt

src/tools/delegate-task/constants.ts

@@ -535,18 +535,31 @@ export function buildPlanAgentSystemPrepend(
 }
 
 /**
- * List of agent names that should be treated as plan agents.
+ * List of agent names that should be treated as plan agents (receive plan system prompt).
  * Case-insensitive matching is used.
  */
-export const PLAN_AGENT_NAMES = ["plan", "planner"]
+export const PLAN_AGENT_NAMES = ["plan"]
 
 /**
- * Check if the given agent name is a plan agent.
- * @param agentName - The agent name to check
- * @returns true if the agent is a plan agent
+ * Check if the given agent name is a plan agent (receives plan system prompt).
  */
 export function isPlanAgent(agentName: string | undefined): boolean {
   if (!agentName) return false
   const lowerName = agentName.toLowerCase().trim()
   return PLAN_AGENT_NAMES.some(name => lowerName === name || lowerName.includes(name))
 }
+
+/**
+ * Plan family: plan + prometheus. Shares mutual delegation blocking and task tool permission.
+ * Does NOT share system prompt (only isPlanAgent controls that).
+ */
+export const PLAN_FAMILY_NAMES = ["plan", "prometheus"]
+
+/**
+ * Check if the given agent belongs to the plan family (blocking + task permission).
+ */
+export function isPlanFamily(agentName: string | undefined): boolean {
+  if (!agentName) return false
+  const lowerName = agentName.toLowerCase().trim()
+  return PLAN_FAMILY_NAMES.some(name => lowerName === name || lowerName.includes(name))
+}