feat(cli,tui): surface /queue, /bg, /steer in agent-running placeholder (#16118)

* feat(cli,tui): surface /queue, /bg, /steer in agent-running placeholder

While the agent loop is running, the input placeholder previously only
hinted at Enter-to-interrupt. Surface the full set of busy-time actions
(interrupt via new message, /queue, /bg, /steer) so users discover them
without hunting through docs or Teknium's tweets.

- cli.py: "msg=interrupt · /queue · /bg · /steer · Ctrl+C cancel"
- ui-tui/src/components/appLayout.tsx: same string (was "Ctrl+C to interrupt…")

* revert tui placeholder change (cli-only per review)

cli.py

@@ -9841,7 +9841,7 @@ class HermesCLI:
                 status = cli_ref._command_status or "Processing command..."
                 return f"{frame} {status}"
             if cli_ref._agent_running:
-                return "type a message + Enter to interrupt, Ctrl+C to cancel"
+                return "msg=interrupt · /queue · /bg · /steer · Ctrl+C cancel"
             if cli_ref._voice_mode:
                 return "type or Ctrl+B to record"
             return ""