9p: reject unrecognized ctl commands

ctl now validates the first word of input against a closed set of
known commands. Unrecognized input returns an error instead of being
silently forwarded as a prompt to the agent.

README.md

@@ -109,7 +109,7 @@ echo "rn my-name" > ~/mnt/ollie/s/<session-id>/ctl   # rename session
 echo "model qwen3:8b" > ~/mnt/ollie/s/<session-id>/ctl
 ```
 
-`ctl` accepts `stop`, `kill`, `rn <name>`, or any command supported by the agent (the `/` prefix is added automatically).
+`ctl` accepts only recognized commands: `stop`, `kill`, `rn <name>`, `compact`, `clear`, `backend`, `model`, `models`, `agents`, `agent`, `sessions`, `cwd`, `skills`, `tools`, `mcp`, `context`, `usage`, `history`, `irw`, `help`. The `/` prefix is added automatically. Unrecognized input is rejected with an error.
 
 ### Switch backend, model, or agent
 
@@ -119,7 +119,7 @@ echo qwen3:8b > ~/mnt/ollie/s/<session-id>/model
 echo myagent > ~/mnt/ollie/s/<session-id>/agent
 ```
 
-Writes to `backend`, `model`, and `agent` are rejected with an error when the agent is not idle. Writes via `ctl` are asynchronous and cannot return errors; if the agent is running, the command is silently rejected. Check `state` to confirm the change took effect.
+Writes to `backend`, `model`, and `agent` are rejected with an error when the agent is not idle. Writes to `ctl` return an error for unrecognized commands; recognized commands are dispatched asynchronously. Check `state` to confirm the change took effect.
 
 ### Kill a session
 

internal/p9/server.go

@@ -1039,19 +1039,28 @@ func (s *Server) handleWrite(path, input string) error {
 		return nil
 
 	case "ctl":
-		switch {
-		case input == "stop":
+		cmd := strings.Fields(input)
+		if len(cmd) == 0 {
+			return fmt.Errorf("empty ctl command")
+		}
+		switch cmd[0] {
+		case "stop":
 			sess.core.Interrupt(agent.ErrInterrupted)
-		case input == "kill":
+		case "kill":
 			s.killSession(sessID)
-		case strings.HasPrefix(input, "rn "):
+		case "rn":
 			if name := strings.TrimSpace(input[3:]); name != "" {
 				if err := s.renameSession(sessID, name); err != nil {
 					fmt.Fprintf(os.Stderr, "olliesrv: rename: %v\n", err)
 				}
 			}
-		default:
+		case "compact", "clear", "backend", "model", "models",
+			"agents", "agent", "sessions", "cwd", "skills",
+			"tools", "mcp", "context", "usage", "history",
+			"irw", "help":
 			sess.core.Submit(sess.ctx, "/"+input, publish)
+		default:
+			return fmt.Errorf("unknown ctl command: %s", cmd[0])
 		}
 		return nil