fix(cli): /stop typed mid-turn shows its interrupt and stop results

Symptom: /stop typed while a turn runs interrupts the turn and kills the
session's background processes, but prints nothing. Idle, the same
command prints "No running background processes." or the stop counts.

Root cause: PR #138668. ecfcf103ad added the interrupt notice on the
prompt_toolkit Enter handler, and 55a8974c13 moved the mid-turn cleanup
onto a worker thread. Both printed with plain print(). From the Enter
handler or a worker thread while the Application runs, a plain print()
races the input redraw and is overwritten.

Change: the interrupt notice and every _stop_background_work line go
through _cprint (the module's _cp helper), as /steer, /queue, /bg and
/btw already do. _cprint paints on the app's loop when it runs and falls
back to a normal print otherwise, so the idle /stop output is unchanged.

Why: /stop is the only one of the classic CLI's mid-turn inline commands
(/model, /steer, /queue, /bg, /btw, /stop) that still printed through
plain print(). The test now checks the lines reach _cprint, because
capturing stdout passes for a print() the user never sees.

hermes_cli/cli_commands_session_tools.py

@@ -119,7 +119,7 @@ class CLICommandsSessionToolsMixin:
             return _stop_background_work()
         if getattr(self, "agent", None):
             from agent.interrupt_compat import request_hard_interrupt
-            print(f"  {t('cli.tui.interrupting')}")
+            _cp(f"  {t('cli.tui.interrupting')}")
             request_hard_interrupt(self.agent)
         from agent.memory_provider import spawn_context_thread
         spawn_context_thread(_stop_background_work, name="cli-stop").start()
@@ -296,7 +296,8 @@ class CLICommandsSessionToolsMixin:
 
 def _stop_background_work() -> None:
     """``/stop``'s cleanup: kill the background processes, then interrupt the background (async)
-    delegations. Mid-turn it runs on a worker thread and prints its result from there."""
+    delegations. Mid-turn it runs on a worker thread, so it prints through ``_cprint``: a plain
+    print() from off the input loop is buried by the prompt_toolkit redraw."""
     from hermes_cli.gateway_tools import process_registry as _registry, process_view
     process_registry, view = _registry(), process_view()
     if view is not None:
@@ -305,17 +306,17 @@ def _stop_background_work() -> None:
     # Background subagents live in their own registry, not the process registry.
     n_async = view.active_delegations() if view is not None else _probe("tools.async_delegation", "active_count", 0)
     if not running and not n_async:
-        return print(f"  {_t('stop.none_running')}")
+        return _cp(f"  {_t('stop.none_running')}")
     if running:
-        print(f"  {_t('stop.stopping', count=len(running))}")
-        print(f"  {_t('stop.stopped', count=process_registry.kill_all(source='cli.stop'))}")
+        _cp(f"  {_t('stop.stopping', count=len(running))}")
+        _cp(f"  {_t('stop.stopped', count=process_registry.kill_all(source='cli.stop'))}")
     if n_async:
         if view is not None:
             interrupted = view.interrupt_delegations()  # the gateway interrupts this session's own
         else:
             from tools.async_delegation import interrupt_all
             interrupted = interrupt_all(reason='/stop')
-        print(f"  {_t('stop.interrupted_delegations', count=interrupted)}")
+        _cp(f"  {_t('stop.interrupted_delegations', count=interrupted)}")
 
 
 def print_session_diff(cli, result: dict, stat_only: bool) -> None:

tests/hermes_cli/test_gateway_tools.py

@@ -133,14 +133,19 @@ def test_agents_before_the_first_turn_reads_the_opened_sessions_processes(gatewa
     assert ("process.list", {"session_id": SID}) in client.calls
 
 
-def test_stop_typed_mid_turn_interrupts_the_turn_then_stops_processes(gateway, monkeypatch, capsys):
+def test_stop_typed_mid_turn_interrupts_the_turn_then_stops_processes(gateway, monkeypatch):
     """/stop typed while a turn runs is dispatched inline and interrupts it like Ctrl+C (tracker
     #134889 N4), instead of being queued until the turn it should stop has finished. Only the
     interrupt runs on the UI thread: ``kill_all`` waits out each process's stop grace period, so it
-    runs on a worker and the input is back at once (Greptile 4277259986)."""
+    runs on a worker and the input is back at once (Greptile 4277259986). Both its notices go
+    through ``_cprint``: a plain print() from the Enter handler or the worker is buried by the
+    prompt_toolkit redraw, so a mid-turn /stop printed nothing (tracker #134889 CLI-27)."""
     import threading
     from types import SimpleNamespace
+    import cli as cli_module
     from cli import HermesCLI
+    painted = []
+    monkeypatch.setattr(cli_module, "_cprint", painted.append)
     _agent, client = gateway
     view = gateway_tools.process_view()
     assert view is not None
@@ -168,7 +173,7 @@ def test_stop_typed_mid_turn_interrupts_the_turn_then_stops_processes(gateway, m
     release.set()
     for worker in [t for t in threading.enumerate() if t.name == "cli-stop"]:
         worker.join(5)
-    out = capsys.readouterr().out
+    out = "\n".join(painted)
     assert stopped.is_set() and "Interrupting agent" in out and "Stopped 1 process(es)." in out
     assert any(method == "process.stop" for method, _ in client.calls)