feat(cli): note background delegate_task dispatch in _on_tool_complete

A top-level delegate_task dispatches in the background and re-enters as a
fresh turn when done. Print a one-line dispatch-time note — no spinner,
nothing to poll — so the idle prompt doesn't read as "nothing happened."

tests/cli/test_cli_delegate_background_notice.py

@@ -0,0 +1,69 @@
+"""The CLI spells out auto-resume when a delegate_task goes to the background.
+
+A top-level ``delegate_task`` returns a handle immediately and runs the subagent
+in the background; the result re-enters the conversation as a fresh turn when it
+finishes. ``_on_tool_complete`` prints a one-line, no-spinner reassurance at
+dispatch so the idle prompt doesn't read as "nothing happened".
+"""
+
+import json
+
+import cli
+from cli import HermesCLI
+
+
+def _make_cli():
+    cli_obj = HermesCLI.__new__(HermesCLI)
+    cli_obj._pending_edit_snapshots = {}
+    return cli_obj
+
+
+def _capture(monkeypatch):
+    printed: list[str] = []
+    monkeypatch.setattr(cli, "_cprint", lambda text: printed.append(text))
+    return printed
+
+
+def test_background_dispatch_prints_resume_notice(monkeypatch):
+    cli_obj = _make_cli()
+    printed = _capture(monkeypatch)
+
+    result = json.dumps({"status": "dispatched", "mode": "background", "count": 1})
+    cli_obj._on_tool_complete("tc1", "delegate_task", {"goal": "x"}, result)
+
+    joined = "\n".join(printed)
+    assert "resume" in joined.lower()
+    assert "it finishes" in joined
+
+
+def test_background_batch_dispatch_pluralizes(monkeypatch):
+    cli_obj = _make_cli()
+    printed = _capture(monkeypatch)
+
+    result = json.dumps({"status": "dispatched", "mode": "background", "count": 3})
+    cli_obj._on_tool_complete("tc2", "delegate_task", {"tasks": []}, result)
+
+    joined = "\n".join(printed)
+    assert "3 tasks" in joined
+    assert "they finish" in joined
+
+
+def test_synchronous_delegate_result_prints_no_notice(monkeypatch):
+    """A non-background result (e.g. the stateless sync fallback) must not claim
+    a background dispatch."""
+    cli_obj = _make_cli()
+    printed = _capture(monkeypatch)
+
+    result = json.dumps({"results": [{"status": "completed", "summary": "done"}]})
+    cli_obj._on_tool_complete("tc3", "delegate_task", {"goal": "x"}, result)
+
+    assert not any("resume" in p.lower() for p in printed)
+
+
+def test_non_delegate_tool_prints_no_notice(monkeypatch):
+    cli_obj = _make_cli()
+    printed = _capture(monkeypatch)
+
+    cli_obj._on_tool_complete("tc4", "read_file", {"path": "a"}, '{"ok": true}')
+
+    assert not any("resume" in p.lower() for p in printed)