fix(agents): block task/sisyphus_task/call_omo_agent from explore and librarian

Exploration agents should not spawn other agents - they are leaf nodes
in the agent hierarchy for codebase search only.

src/agents/explore.ts

@@ -28,6 +28,9 @@ export function createExploreAgent(model: string = DEFAULT_MODEL): AgentConfig {
   const restrictions = createAgentToolRestrictions([
     "write",
     "edit",
+    "task",
+    "sisyphus_task",
+    "call_omo_agent",
   ])
 
   return {

src/agents/librarian.ts

@@ -25,6 +25,9 @@ export function createLibrarianAgent(model: string = DEFAULT_MODEL): AgentConfig
   const restrictions = createAgentToolRestrictions([
     "write",
     "edit",
+    "task",
+    "sisyphus_task",
+    "call_omo_agent",
   ])
 
   return {